Everyone is kinda biased for a character, because they identify most with them or just focus more on a character. Thats not an issue, its not even bad, it can bring up different point of views, which is always an interesting thing.
The point is, some people want to debate to learn more and read something about different point of views and some people just want to on a "winning side", just want their character to win.
There is just a difference between biased and illusional.