A snip from an essay well worth reading in full, otherwise offered without comment:

… the issue isn’t negativity per se, which has its place in the fandom ecosystem. The issue is how to talk about things you love (or hate) impersonally. What is lost in fandom is ultimately detachment. Detachment can coexist with love, hatred, and indifference. But it’s never an especially attractive quality, and when people are encouraged to identify themselves with their interests and consumption habits, it’s also a very hard one to maintain.