Is this in any way bannable?

the flame is reportable yea. the banning your teammates champ isnt

Banning a teammate's pick, on its own, is not bannable. There are strategic reasons to do so. I personally don't condone it, and I disagree with Riot's stance on it, but there you go.

Cursing at you for no reason in champ select is toxic behavior. And if I'm understanding correctly that the first and fifth players on your team were in a premade and both conspired to ban your hovers, I believe even Riot considers that to be trolling.

the action of banning isn't, but the attitude behind it points towards a direction of negative attitude. Over many games, if he kept up with that speech, he'll get punished for it.