You said, and I'm quoting here:
I spent 3 years in uni being screamed at, in my face often, about how awful I was for being white and working class guy. Glad you didn't have that experience? But plenty of men do. But it was really hard not to become totally alienated by that. A few times I was threatened physically, because I 'don't look leftist', whatever the fuck that means. I still occasionally have some nutbags approach me and scream at me about my perceived politics based on how I look.
You're being challenged on this because the vast majority of white working class guys simply don't have this experience whatsoever. This whole "leftists screaming at your face"-thing seems to be pretty uniquely happening to you, not white men in general.
So this does beg the question: why do you have this experience when other white guys in this thread don't? You've immediately resorted to blaming leftists in general, but since others don't share your perception of leftists you're simply not very convincing.
It's like arguing that the far-right grows because the left shits on the street; nobody else seems to have seen this so people end up questioning your sincerity here.