Look it up yourself. Paul Graham does not have a core competency regarding what smart people are or are not willing to do. That would be sociology or psychology or economics.
Just realised that this is a subtweet of PG's post.
So I think what he's saying here, with some brevity, is: startups require lots of smart people to succeed. If the boss isn't nice to them, then those people can easily find work elsewhere. Therefore, the boss will have to be nice to them. Therefore, the boss can't be a horrible person.
Therefore, the boss will have to be nice to them. Therefore, the boss can't be a horrible person.
You should study up on logic. You are saying that since person A has to be nice to people who work for startups they can’t be a horrible person. This means that if a person is horrible they can’t be nice to people who work for startups. This is egregiously wrong.
I think what PG is saying in this situation is, he's using "evil" as shorthand for "is not nice to their employees", whereas you're reading it as "is fundamentally bad in every way".
We might also want to delve into what "evil" means here. Presumably he's talking about evil in the way that they treat their employees?
As sibling says, that's his core expertise, so not quite relevant.