If a single person solves 0.01% of the world's injustice that's a huge success.

It looks to me as if you just switched from one 99.99% to an almost completely unrelated 99.99%. I see no reason to think that Paul Graham or AirBnB has solved 0.01% of the world's injustice. Even if they had, finding 10k Paul Grahams or 10k AirBnBs is not at all an easy problem.

Startups funded by YC fight powerful enemies day-in-and-out by disrupting industries.

You don't get points for fighting powerful enemies, you get points for doing actual good. No doubt some YC companies are in fact improving the world; good for them; but what does that have to do with the question actually under discussion? Viliam never said that YC is useless or that PG is a bad person. He said only that PG is focusing on one (important) part of reality -- the part where some people add value to the world and get rich in the process -- and may be neglecting another part.

There's no glory in fighting for the sake of fighting.

Of course. Nor much utility. So the question is: if there's a lot of injustice in the world, is it effective to point it out and try to reduce it? Maybe it is, maybe not, but I don't see that you can just deflect the question by saying "effective political action is a matter of building effective communities with good norms".

You change things for the better by providing powerful alternatives to the status quo.

You're just restating your thesis that in the face of evil one should construct good rather than fighting evil. But sometimes you change things for the better just by saying that the status quo isn't good enough and trying to get it knocked down, or by agitating for other people who are better placed than you are to provide powerful alternatives to do so.

Rosa Parks didn't start her own non-racist bus service. She helped to create a climate in which the existing bus service providers couldn't get away with telling black people where to sit.