Because they get shit on constantly. Last year when OW had a "Block this player" feature people abused it to where Widow mains would have wait times longer than the days when Evolve only had 200 players on PC.
Then recently a defense main (I think Torb) got banned juts by playing torb.
Then some Sombra mains have been getting muted because of the players abusing the report system.
While it's not limited to defense heros, they certainly get most of the shit.
There is a different between playing a hero that you're good at from the start of the game and switching to a hero that you have no time on (thus defense heros).
I'm talking about reporting based on picks, not based on actions.
I didn't mind him after his hook 2.0 as it actually gave some sort of counterplay. All Hog needed was a counter other than himself and Ana. But the people who bitched about the hook combo were the same who bitched about it "reaching around corners and ledges." It's a never ending battle, and that's why it's a joke; it's all a joke.
Blizzard can't even balance a game without player complaints getting through. This all makes Kelder look like childs play.
No, what people didn't seem to understand was that Hog's power is ALL built around that hook. It's the reason why he has a self heal. It's the reason why he had a shot firerate shotgun with huge spread. And now that Blizz is trying to rearrange the power in his kit it's showing how broken he is without it. Once again, a baitable hero that only needed a few counters, and Mei, Reaper, and Bastion were good starts (even Torb and Sym with their armor and shields), but hook 2.0 gave him the power to one shot those heros, is where Blizz crossed the line, just like when they have Dva 100 extra health on her mech.
There's also a lot of other one shot mechanics in this game too, and a glance at Widow shows Hog 2.0. Hog only had the combo, but most people play widow for her looks. Then next to her, Junk's trap and tire, Dva's ult, McCree's fth, Zen right click.