Banning Pick Intent Unsportsmanlike
I feel that, in a lot of circumstances, banning a champion that someone shows pick intention for is definitely unsportsmanlike and should be an offense you can report someone for. I understand if I'm last pick and want an OP or overplayed champion and my team can't trade them to me then yes, ban away and all is good. However, if I am first overall pick and want to play an OP champion (that I'm presumably good at) you should not ban them because, at that point, you are just trolling your team. It will cause me to get irritated that you felt the need to ban a champion I would have been 100% able to secure and a champion that may have been my best for the role. Another time that it is fairly troll is if you ban someone's main champ. I'm talking having Annie Bot on your team and banning Annie or anyone that has a champion's name or reference in their summoner name or clan tag. For apparent reasons you should not ban that champion. Recently I had mordekaiser banned away from me as a mordekaiser main in the mordkaiser club with MORDE as the clan tag... According to lolking mordekaiser has a 2% play rate so there is a very small chance the other team would pick him and if you don't want mordekaiser on your team because he's bad (which is why they banned him) then the other team taking him shouldn't be a problem. I personally have a 59% win rate on mordekaiser through almost 300 ranked games on him and climbed from silver 4 to diamond 4 playing 75% of my ranked games on him. So banning mordekaiser was a hindrance to the team whether he liked it or not since it forced me on a champion that I am sub-par on which, statistically, means we had a less of a chance of winning because you felt the need to troll and ban my champion because you don't want to play with mordekaiser.
TL;DR Think a little before you are going to ban someone's pick intention as to whether or not there is a good chance the other team can pick them beforehand (if the are OP) or if you are considering banning someone's main away. If you ban because you don't like their pick you are being unsportsmanlike and should be reported as such.