It's not culture (organic), it's systems (planned): if you don't, on day zero, agree what code reviews should cover (and what not), then code reviews are a pissing contest first, and a useful tool second.

I noticed a lot of people don't understand both the limitations of code reviews, and what issues they can and should solve. Writing good critique (of anything, not just code) is hard, we don't train people to do it, and usually don't even regard this as something that needs training and understanding.