Whether or not anyone else wrestles with their SO isn't really the point, if they are both freely consenting to the behavior it's their own decision. I can understand not wanting to watch, and if it were occurring in a public space, the living room, dining room, kitchen, the it is certainly reasonable for the roommate to object to their choice of location. On the other hand they were doing it in what the roommate represented to them as their bedroom. I think it is rude to peek into your roommates bedroom and set rules around what they can and can't do there. Dictating behavior in the bedroom is very close to saying that your roomates scrabble moves are not the ones you approve of so they must leave.
If they felt they had to object, then at the least they could have said that the wrestling disturbed them and could they avoid doing it while they were around. If that weren't sufficient for them, then they could have asked them to avoid it until they could find another place to live, which is still better than kicking them out abruptly.
Telling another couple that their relationship is unhealthy and disgusts you is, I think, always rude. Even if you feel that your disgust is justified, it's still rude to tell someone that.