Going with the comment by Vylix and addressing the "offended" question, I support the answer by apaul34208 and add in some thoughts.
Since you stated there's no trend into what does and doesn't genuinely offend me, it seems that you can learn more about yourself from these encounters.
You can tell yourself something at that time to remember the comment, and your feeling, in the moment, so you can think about it later. When you have the time to think about it, ask yourself:
- What was said that I was offended by?
- Did they mean it as offensive, or was it part of the joking?
- Would other people I know find that offensive?
- Would I always find that offensive?
- Do I want to always be offended by that?
- Why did that offend me?
- How did I really feel when that was said?
- What in my system of values made that offensive to me?
- Is that something I want to have in my system of values?
Use your own answers to these questions to learn more about yourself, and what you value in life. You can also see if there is something about yourself that you want to change to grow into an even better person.
Later, in future encounters, if that still offends you, and you have decided that being offended by it is appropriate, and you want to say something about it, it can help how you say it. Being "offended" is a cover emotion for some other feeling, such as feeling disrespected, or threatened. Having answered the above questions, you now know how you feel about that comment and can say something like:
I feel ____ when you say _____.
That is better than saying you are offended, which can be hard to translate for them, and it's owning your feelings, telling them why you feel that way without blaming them for your feelings. Since they aren't being "blamed" for your feelings, they are more likely to respect your feelings, and try to modify their comments.