The behavior he's calling "heresy" here cannot be evaluated in a vacuum; these kinds of statements are all contextual, ESPECIALLY hinging on who is saying them. And the reason that is the case is because the consequences of saying something are different depending on who says them.
Paul Graham is wealthy and influential, and actively tries to influence folks with essays like this. So when he says something, it is judged in a harsher light because those words have a much stronger effect than if, say, some L2 software engineer on Twitter said them. If PG says something that _could_ be interpreted as racist, it threatens to normalize believing that in the minds of the people who follow him. If L2 says something that is on the fence, at worst some of their immediate friends will pile on to them about how uncool that was (barring the rare occasions of people going viral for bad takes, which is an outlier).
I think that's reasonable social policing to keep our discourse healthy. Having that influence over people demands a price in return. If PG wanted to stop getting pushback for approaching what society thinks is an acceptable line, he totally can, he just needs to rebrand and get out of the startup game.