My suspicion is that most people who are on the forums complaining about their ban is that the do not realize how much they actually report. They don't realize how they treat people in game. Or, they are simply lying about how they report.
Even the inactive posters suddenly returned to yell murder about this new initiative.
People just love to complain, no matter what Riot does.
Riot doesn't ban players for false reports?
'OMG, Riot, people threaten to report me without consequences. It hurts the game'.
Riot bans players for it:
'OMG, Riot, how dare you ban players for something that was not stated to be a punishable offence? How could you ban players that threatened to report and tried to get others falsely banned?'
See: Onihero. The biggest hypocrite on these forums. He always claimed that Riot had to do something about report bullying.
Now they did, and he has been one of the posters who yells murder to Riot.