For all the support/jungler love, it still has it's bad players
What do I mean by bad? Pretty much any way you want to put it. Toxic, mechanically, anything really.
Usually on the boards there's always 1 thread on the front page thanking supports for all they do because people don't appreciate it in game.
Now personally, I usually stay far, far away from bot lane because I don't like relying on other people, and I just got out of an ADC game and know exactly why they flame sometimes. I didn't say anything rude to my Blitzcrank, I just told him after about my 6th death he should help me more (he spent most of the time in the middle lane helping out mid laner. Nothing wrong with that, he was getting our mid fed, but I was suffering greatly for it). Throughout the whole game really he sort of blamed me for not being able to finish kills he tries to get us (we all got wiped pretty early on, me, support, and jungler).
Basically what I'm trying to say is that yes, there are bad supports out there, and when you NEED that player to be good, it's frustrating.
Support is a very important role, and they definitely deserve respect, but I honestly don't see ADCs hating on their partners THAT often. One in every 5-10 games maybe. But that's just a general rager, he could be going top and blame the jungler either way.
I'm not saying you should and can rage at your supportive roles, I'm just saying that NEEDING them, and them letting you down is a huge blow to morale, and I understand why people would rage.
Don't pretend you aren't frustrated when you jungler dives and gives your opponent double buffs.