I think that as long as riot allows people to spend money on its game it should not have the ability to permanently ban people for any reason other than hacking/cheating. Personally, I would never spend money on a free game like league but a lot of people do. The internet and league are full of trolls who will bait people into saying things on chat that riot might ban for. Because riot issues bans so easily and a lot of people spend a lot of good money on its game, I dont think permanent bans should be a thing for anything other than hacking/cheating.
Just putting in my two cents