There is a similar question here: How to tell someone believing in pseudoscience & conspiracy theories is wrong without making them feel stupid/upset? My question has a different setting: I'm dealing with a person who is not my friend or family member.
Situation: I was talking to a guy (an acquaintance who I have some common business with, not related to job) about sex-related topics and I asked him if he knows that syphilis can be transferred via kisses, and he responded with a bunch of nonsense. He believes that "syphilis is a gene of the negroid race which helps to deal with high temperatures and that if a woman is infected, she will have a specific scent." (My rough paraphrase of his words.) That is obviously all false.
The problem is, he seems to have rather chaotic sexual habits, and I believe he might end up having some STD. He mistakingly believes that he can tell if someone is infected and take some actions to prevent the infection.
- At the minimum, I want to tell him he's wrong, but I can't (and don't want to) spend too much time on it.
- Ideally, I'd like to teach him something about reputable sources of information and how to spot urban legends, pseudoscience, etc., but I don't want to give him a lecture.
- I already told him what I know about the disease, but he replied with, "I'll find the info later [and show you]." He seems like a stubborn guy, and I hope there's a method to present the information vividly, in a way which he wouldn't want to argue with.
- I don't want to be rude, but I'm not really afraid of upsetting him. Our relationships are somewhere between "colleagues" and "bros," so he's okay with informal conversations.
That is not the first time I hear this kind of bizarre "facts" from him, and since we'll probably communicate for a while, I'd like to do something about it, partly because I care about him a bit, and partly because some of his "myths" affect the way we do our common business.