I had that theory for why I was banned from youtube. The more I thought about it though, I couldn't come up with any reasons for large corporations such as youtube/twitter/facebook to pick sides in sports.
It's probably just lazy moderation/administration on their part. I'm trying to avoid using insults on my new account, even when they are deserved or in retaliation to some(not always successfully). Consider every comment to be taken in isolation with no context, when someone reports it. Feels like some are fishing for a response and then have the audacity to hit the report button. So perhaps just hit the report button(if there is a valid reason), reply only on the subject and see how long they last repeating the same trick.
One mild insult on it's own seems a weak justification to ban/deny service to a member though. I also do think, the fact that they can silence who they want without justifying it, needs to be monitored. It does seem as though they could be censor who they like, with no justification, if they wanted to get involved in politics and sway opinions.