Just cuz they are dead doesnt mean they dont deserve a level of respect. That said, I would be delighted if some strangers thought my grave site was a prime spot to fuck. I just wouldnt want people pissing and shitting on it, thats about it.
If people can have fun where I am buried I would consider it an honor. BBQ, Drink a beer, have sex, fall asleep, w/e. As long as you dont actually deface it. Not that it would matter to me when I am dead anyway, but still.
For the record, if I hate to choose between being raped then killed or being killed then necro-fucked, I will take the 2nd senario.
Depends who is raping you.