Let's talk about banning someone's hovered champion.
I had a very rude person call me an idiot and a troll for voicing my opinion that I should be able to ban any champion I want. There are what, 140 champions now? I ban this champion so I can have a fun game, and I mostly play normals. I don't like this champion on my team or on the enemy team.
I don't ban this champion to be a dick. I ban this champion because a game is meant to be fun. I, personally, do not have fun with this champion on either team. This is EXACTLY what bans are meant for. They are to allow you to remove champions you don't like from the game.
If someone hovers this champion, I ban it. I tell them, "Sorry, I always ban this champion. You may check my match history for proof." I've even gotten shit for this. If it was Yasuo, I feel like people wouldn't care. But as soon as it is a champion which no one tends to ban, everyone loses their minds. They think I MUST do it to troll them, when really it's just to preserve my own enjoyment of the game.
Yes, I think it's acceptable to ban a teammates champion. They have hundreds of other champions to choose from, and in normals it doesn't matter if you're a one-trick or not. I get ONE ban. Just one.