Unsafe sex

Is there a point at which the way a person acts is considered to be SO outside of what is considered "reasonable" that those that "know" them, finally say that person is no longer the type of person they want as a "friend"? Recently, I decided to post this about someone I had the misfortune of getting to know and their behavior has made me want to get this off my chest. I think I am showing enormous restraint in NOT giving their names.
Here is the situation. I met a female online about a year ago, and, after I moved, met her in person. When we were talking about the job situation, I told her that the company I had just started working for was looking another person, she asked me to see what I could do. So, I got an application, called her up, met her at McDonalds, had her fill it out, and turned it in. I pestered my boss until she got an interview, then pestered my boss even more until she was hired. I'm not saying I was the sole reason she was hired, but I think I had alot to do with it.
Now fast forward some time, and I meet her "boyfriend". This guy is 37 and dating her, a 22 year old. Not to say anything about "love has no age" but that's 15 years difference. He met her in a bar, and they had sex that very first meeting. Now, to back up some, this girl is known a bit as a "party girl", which is a nice way of saying she has had more men in her than the Army. So, they do the deed, and you'd think that all is well. And if all was "normal", I wouldn't be on the verge of a rant.
All is NOT normal. Turns out, drunken sex not withstanding, the guy had the presence of mind to wear a condom. Not to avoid pregnancy, but because he didn't tell her he had HERPES. Oh yeah, the gift that keeps on giving. For those of you that don't know, there is NO cure for Herpes. And yes, left untreated it can kill you. So, this guy has the PERFECT trap. He had sex with her quite a few times, then explained to her WHY he always wore a condom and wouldn't have sex with her at certain times ( due to having an outbreak ) and she was fine with that. Then, one night, he got her very very very drunk, and they had sex WITHOUT a condom. And you guessed it, she got herpes. Congratulations.
Now, back to the present time. This guy takes this girl out to bars and "chat parties" and at these functions, he gets drunk and accuses her of wanting to have sex with someone, and then accuses someone there of wanting to "take her from him"and have sex with her too. Well, if she has the decency to inform them BEFORE sex, not a single guy I know of, and not single woman either, would agree to have sex with the risk of incurable HERPES, for a one nighter, or even for a weekend of sex. So, he's causing a scene and being a complete asshat for NO GOOD REASON. Other than, it gets all the attention on him.
They got married, yay. For him, it's the perfect arrangement, a woman at home for sex and to keep his place clean; for her, she ends up with the guy that infected her and leaves her with no choice but to be with him, because he already has it. God forbid they have kids, because the risk of transmitting it to the child is pretty high, and it can cause all kinds of birth complications.

I guess my issue is thus: Should I tell people that these two, particularly HIM - because he does present himself as being such a "sexy guy", and talks to some of the females in the group about threesomes and such - that he's carrying a loaded weapon? Is it my responsibility to inform them, since he obviously doesn't have it within him to do so? Or do I simply walk away and live with the hope that I never meet someone they might have had sex with and have to worry about catching that disease myself?