My point is - copyright is also a "content related" reason: some site is banned because the content of the site is infringing the copyright of someone else.

In the end, all censorship is content related. One could definitely argue along the spectrum of "all" to "none" censorship is appropriate, but I would guess most people actually hold the belief that "some" censorship is okay, while disagreeing on "which" censorship is okay.

If this is the case, then the bias problem is indeed relevant.

Copyright is a content-based reason.