Rape is just nasty on all sides. It's the most devastating of crimes if true and the most devastating of lies if false.
In any number of rape / sexual assault charges the basic argument from the prosecution is "Why would she lie about this?". And it's a very effective argument, even when there is absolutely no other evidence.
This is why it's chilling when 6 guys are saved by a video tape. You must ask yourself - What if there was no tape? Nobody would believe the six guys.