Here's one allegation. Worth reading through all the comments to get the measure of the man's depravity. Sure sounds like a nasty piece of work...

"Back in the late 90s a straight male friend of mine thats a film maker met him at some industry event in NYC. He got talking to him, thought he was really cool and all. They left the party and hit some bars and got amazingly drunk. My friend thought it would be easier if they crashed at his family's place nearby rather go back home. He woke up in the middle of the night to a terrible ruckus. Seems his new "friend" sneaked into the bedroom of his 14 year old brother and was trying to remove his pants. Little bro woke up and clocked him right the face. Spacey ran out of the place. Prior to all this, when the two were drinking, he learned that Spacey was due to attend another event the next night that my friend was also invited to. Spacey was a no show the next night."

https://www.datalounge.com/thread/10510884-kevin-spacey