PTSD affecting certain friendships

what happened is this:

i was sexually assaulted about seven years ago by someone i barely knew and had no interest in. this was shortly after i started hanging out with a brand new group of people, some of whom are now very close friends. the guy that assaulted me was friends with some of the people in this new clique and that's how i encountered him.

like a lot of other assault survivors, i did not tell anybody what happened immediately afterwards. my silence was further entrenched in this situation because, well who were they going to believe- the new girl they barely knew or the guy they'd known for a while (even though there were quite a few people who didn't like him)? also the perpetrator was very conniving and persuasive and was able to make it look like we were dating, when in fact he was assaulting me repeatedly over a two week period. if you think i feel all the more powerless knowing i was not able to physically get away from him or outsmart him (as some other girls who he attempted to do the same thing do were) for all that time, you're right.

anyway, to this day almost no one knows that happened. for the people in that group that i'm still friends and talk to more than occasionally, they know (through my boyfriend's telling them) to not bring up this person's name or anything about this person around me because it causes distress. mostly they respect that, though they don't my exact reasons for this request (and it's good that they do because the PTSD-type feelings that can come up are severe- and for the record, yes i am in therapy for it).

my current problem is that some of these people remain friends with this guy (and who am i to stop them?). from their points of view (not knowing about the assaults) they know i can't stand him but that has nothing to do with them. i'd feel extremely uncomfortable disclosing what happened to these people for fear that they'd accuse me of being dramatic/crying for attention (though i'm not one to be that way and i would think they'd know that by now but who knows) or of digging up old baggage (from the point of view of my mental health, it's something i still deal with but from their point of view, it's seven years ago and is water under the bridge). also, the couple people i'm really talking about still seem to have this idea that i was "with" the perpetrator for that time, despite my having told them otherwise several times. but without intending to, i'm starting to have a 'guilty by association' psychological reaction to these people at times, and i've wondered if (as bad as it would make me look) it would be in my mental health's best interest for me to stop communicating with the one or two certain people who are/were very close to the perpetrator.

i know i can't expect much sympathy from them when they don't know what happened but as i've mentioned, i have my worries about telling them at this point and if i told them it could open up a can of worms worse than the one i'm struggling with now (in the worst case, possible revenge from the perpetrator).

i recently had to permanently cut off a formerly close friend, who did in fact know what happened, due to the fact that she'd disrespected my requests and pleas to her to not talk about this person around me one too many times. the final straw there was when i called her out on bringing said subject up without thinking, and she apologized, but then less than five minutes later- no exaggeration- she was merrily bringing up this person again with another friend who was there, and she had a huge grin on her face. i think she thought she was being somehow clever because all she was doing was avoiding mentioning his name and she thought she could get away with doing that. to make matters worse, this scenario took place in my own home when i was letting her stay. i subsequently kicked her out and cut off all communication with her. she was of course very upset, crying away that she was being "singled out" and she didn't know what she had done (even though i'd told her plain and simple). what made a tough situation even more upsetting there was the third friend who was present for all this initially chided me for being too hard on her and that my sudden cutting her off made me look shallow (i honestly don't understand what that had to do with anything at all and my cutting her off was far from sudden as i'd warned her before and given her a clear request just moments earlier. but i didn't have the energy to respond in any way that could lead to an argument. needless to say, i found this friend's reaction akin to rubbing salt in an open wound)

anyway i'm just so unsure of how to deal with this situation. how can i move on from this terrible ordeal i faced while remaining friends with people who've done me no harm but who are unknowingly connected to the trauma?