Ok, this is just simple interpersonal relations and it goes back to middle school. When someone insults you or something you care about, and you show your discontent and get grouchy, you're only inviting more ridicule. I actually have a lot of friends back in the States that call it "man wrestling" because they want to bust my balls about it. I just call it man wrestling as well and laugh WITH them. If you don't take yourself so seriously, it won't be such a sticking point.
When people call it barbaric (or infer that), I often point out that "you know it's funny, because I had that impression when I first started, when I was simply in it as a learning experience. Turns out most of my classmates have a higher level of education than people I know from country clubs, gym, etc." Then I'll explain how so many of the guys I know from BJJ are PhDs, Attorneys, NASA employees, medical doctors, MBAs, etc. In addition, I will make comments that close the gap. For example, I would say "it's actually quite similar to golf in that it's a thinking man's game, similar to chess but with leverage as the foundation. You will see students defeated by people 50-80 lbs. lighter because the superior BJJ player is better with technique or a quicker thinker. It's much easier to understand if you observe it in person. You should come see it"
Personally, though, I have to admit that I am hesitant to mention BJJ at work unless pressed, b/c I'm an attorney and the stigma, regardless of justification, remains. It is, ultimately, combat and people will see it as such because people are mindless dullards who are intimidated by it and often denigrate it because calling it "barbaric" is a good way for them to deflect their insecurity and/or lack of understanding via acting as if they're "above it" themselves.
As far as the herpes comment, you should just tune out immediately and just hand the guy a cat toy so he can amuse himself.
