I have practiced several martial arts. In one of them I got close to get a black belt. However I was never interested in really violent martial arts, so I didn't have to deal with blood like you describe, because once I noticed the level of violence, if I wasn't comfortable I changed class. But I had to deal with other kind of issues. I practiced Aikido, for example, where you don't see blood but if you deal with really violent people they can snap one of your articulations easily, or hurt you badly. Sometimes I managed to get the other person to listen to me, sometimes I didn't. It depends a lot on the other person, but I followed, in general, the steps I described bellow.
I understand your point of "I-know-everything-better-because-I-am-the-black-belt", it can be quite a problem. In some cases, no matter what you do, you won't be able to get pass that, in which case I would recommend to change instructors/class altogheter.
The issue you describe can be considered a "man up" kind of problem. What I mean, is that there is a likely chance that if you go and complain about this they are going to respond in some kind of way suggesting you need to man up. Note that I don't consider it that way, I am describing how the instructor most likely sees it.
Taking into account what I said, first step is finding a way to avoid the perception that you are weak, basically building trust in a way a instructor like this would respect. That is why I asked how good you were in this Martial art. People have a tendency to listen more to people they respect. Think it this way, you have been doing something in a way for a long time, one day someone new shows up and he tells you that you are wrong, you won't take that nicely. That is why you need to build trust and get him to see you like the sport.
I would suggest you to go to a couple of classes and show your skill, kind of go all out, without bleeding, or if you are bleeding, step aside and take care of the injury and then go back to fight all out, leading by example. The goal here is to make him see you are not weak, and you like the sport.
Next, or at the same time, however you see fit, ask him stuff. Show you really care. For example, it depends on the sport. But in Aikido there are variations of the same "grapple" (i think that is the word? basically how you go fend off an attack and how you turn it against the enemy). So you could ask better techniques, or discuss reasons for how it is done or his opinion of some particular issue. If this sport is also a competition sport, watch and comment about it. The key is to build rapport with the instructor, and find common ground. Like If I had to deal with an Action movies buff, I wouldn't talk to him about Heidi, I would talk to him about the latest John Wick movie.
Once you have proven you are not weak, and have built some rapport, you are in a position where he may hear you out. At this point you probably know his routine, and you know when you can find him and talk alone with him. So as @Allerleirauh suggested I would talk with him alone, because that way he can be more receptive of what you may have to say. Take into account that all that bleeding nonsense, is probably related with the perception of weakness, so this guy wouldn't take kindly to anyone placing him in a position where he could be perceived as weak. Is either that or he is really sort of a "distracted"/scatter head kind of person, so he wouldn't take lightly either to be put in ridicule.
Remember, he is an expert on the martial arts, don't question his expertise. Avoid at all costs talking about the sport itself. Never mention the martial arts, talk about the health concerns in the modern day. But take also into account, that some Martial arts groups become a bit of a family. So you don't throw shade on the other practitioners either.
So avoid saying things like:
I think is great to practice all out but I think we are overdoing it
That is bad because you are questioning his expertise in the martial art.
Look, the other day there was blood all over the place. It really
worried me we could get a disease transmited by blood.
That is bad because you are attacking the family. Family doesn't have blood diseases. I know that is not true, but that is the way some people get.
So, how do you say this and have some chance he will listen? Well at this point he respects you because you have shown you like the sport. He likes that you respect and ask for his opinion and expertise. And he has seen you interact with the rest of the team, you are part of the family, or getting there. Don't throw this out of the window. Build on it. Be personal, but follow whatever style of comunication is handled on the dojo. It would be better to use his name, BUT if that is not acceptable, use sensei or whatever the word for your martial art.
- Jonh: this is the best option if available, you are building on friendship here.
- Sensei/Teacher/[Correct word depending of your martial art]: this other options show respect but puts a distance between the two of you. It may be the best option depending on the kind of instructor.
First ask in a polite way, but without making a big deal out of it that you want to talk to him.
John/Sensei, can I have a moment? I wanted to discuss something with
If he is busy, or says he doesn't have time, respect, and try another time. Act like is not a big deal.
Then express some positive feelings about the sport and the dojo, the people practicing and even your instructor. Something along the lines:
I love practicing here, I think I am getting a lot out and I am
improving. I would appreciate that you push me harder that I
have ever been in the past.
Next the tricky part. Do not say "but" or "however", after the nice things you said. If you say those words (I call them the connectors of dead), or similar, you throw everything nice you have said until that point out of the window. You need to link the next part in a way that doesn't take away from what you just said. It would be better if you hesitate a bit before saying something else. This could prompt him to ask you if there is something that is bothering you. But if he doesn't say that you say it yourself.
So say something showing you care for the team and don't mention anything about the sport itself. Don't mention what you have seen done in other dojos, do not compare this dojo to others.
There is something that has been bothering me a bit, in the practices
we go all out, and I have noticed some times there is a lot of blood.
Don't get me wrong, no pain no gain, right? I am just concerned that,
we never know, it can happen to anyone. You meet someone, go out, and
damn you get something. You get me right?. I think sometimes we don't
notice it because we are so engrossed in the practice. I want everyone
to be safe. I don't know what you think?
Up to here, I didn't mention this. I don't know if you are a girl, and I think he is a guy. However she may be a girl. The way you speak varies a little if you are 2 girls, 2 guys, 1 guy - 1 girl. And I am using these words in the really ample sense, there are more variations. You will be more like "girrrrlllll!" in certain situations, you will be more "I am a man I do man things" in others. Fine tune what you say according to that.
For example I am a girl and I always had male instructors. I would be less crude, and play more in the implicit. If I was a guy, I would be a bit more crude. But just if I saw the instructor to be that kind of person. My point here, imitate the communication style, without abandoning your essense. You need him to understand you, not you to become another person. There are more chances he/she will understand you if you speak in his/hers terms, than in yours. But if you would never say the word "shit", don't say it. For example. In the sample paragraph above I said "you go out, and damn you get something", I could have said "you go out and shit happens". Just to give an example.
Notice how, in my example I didn't lay out a plan of action. Just say what what is bothering you. Without really saying much. Let him connect the dots, and if possible, let him decide the plan of action.
- If he suggests the solution: it will be more likely that he will implement it because he is the owner. He will respect for speaking out and showing concern for your team mates.
- If he doesn't say anything, or if he is really vague about it, and you are sure he heard what you said, drop the subject and move on. Later on class see how he reacts if the same thing happens. He may not say anything, but he may do something.
- If he is rude, just reciprocate in jest. Say something like "look dude, I just didn't want to be covered in someone else's blood". Joke a bit and move on.
- If he asks, perplexed or in earnst: Suggest something, remmeber all the tips above. And whehter or not he agrees move on.
Don't press too much, or he will think you are pushy, and see it as a sign of weakness.
Once you got your answer, wait a couple of classes, if the situation repeats and nothing has changed, move on to another class. You tried your best for you and for your team mates. And I have been saying team, because in many dojos people act and feel like are a team.