As someone who applied to every YC company in my region, I find their funded companies do lots of unsavory things. I stopped buying from one because they were using deceptive marketing, and I stopped applying to one after the Glassdoor talked about the long hours and racist incidents.

There's a kind of YC culture where they believe nice guys do well [1]. And they're likely biased towards funding nice people. But after they're funded, they don't really have any control over the company.

[1] http://www.paulgraham.com/good.html