I don't even play support or ADC, but the pattern I've noticed is that supports have the largest concentration of toxic players. They believe that because they are the support that they are entitled to play ANY champion in that role. That they are entitled to build ANY item even if it means skipping gold income items and vision. That EVERYTHING is the fault of the jungle if the jungle doesn't camp their lane. That their ADC is stupid the instant the ADC makes ONE mistake. And that they are entitled to kills and all the CS the instant the ADC dies or fails to secure a kill.
That has been my experience.
Even players who pick actual supports have treated their allies like crap. Regardless of what position they play.
If I am top, it's my fault because I either took ignite over teleport or because I don't teleport down into bot lane often enough.
If I am jungle, it's my fault because I don't camp bot lane all game long.
If I am ADC, it's my fault for not making an enemy go from 100-0 in 2 shots with only 1 or 2 complete items.
Just earlier today I had a support needlessly harass the ADC simply for choosing Varus. They constantly insulted our ADC from champion select until the end of the game and then claimed not to have been toxic at all and to have simply pointed out their version of the truth.
This whole mentality that supports have it hard and that they get blamed more than they deserve is way off. They are people like anyone else in this game and a good number of them are intolerable in game.