I had this happen three champion selects in a row.
First time because i didnt give the guy jungle, when he got queued into bot lane.
He banned who i was going to play as my one and only match of the night (Fiddlesticks) so i went shaco and snowballed top and bot anyways.
Second and third time was a guy banning Shaco because i had it champ previewed as Shaco top and he asked me to pick someone else, even though we already had two people planning to be tanks. So because i asked why he just outright banned shaco and said he didnt want a 'runaround/troll toplane' even though its not my first time playing the champion whos third highest in mastery out of all my champs.
Someone dodged that match because i told him i was going to annoy him because of what he did. and i requeued after waiting a few seconds, i get in champ select with the same guy, he instantly notices me and bans shaco even though this time i got jungle, and was actually planning to go fiddlesticks jungle like i wanted to do for the first match.
He ended up feeding with his troll buddies in bot and mid lane. And now i wish i could punch this guy in the face, because not only did he piss me off by banning my first game because he didnt think shaco top would work, but he got completely steam-rolled in bot lane.
They need to do something about people banning champions out of spite or trolling just because of someone previewing it in their selection.