Largely because you can't speak with confidence. You have made an art out of demonising people and acting on repugnant caricatures when it comes to forming opinions. You have to understand a people on the individual level as well as a group to make a fully informed judgement.
An example: In America in the 1950's and 60's, the stereotype of black Americans was "stupid, violent welfare parasite". On the collective level, this seemed confirmed; violence and crime was rife in black communities, there was high unemployment, and average IQ was lower.
But once you got down to the individual level the grain of truth in the stereotype became clear; there was little emphasis on black education, (and in the segregated south, black schools were often burned down), the institutionalised racism led to employers favouring white job applicants, leading to poverty and the resulting crime.
I think Nobody made a valid point about the nazis and depending on second-hand sources to form a judgement, but these targets of yours (fags, liberals, muslims) are not part of history, they are all around you, and it is a point of vital importance that you interact with them, because otherwise you allow your perception to become skewed, you degenerate into bigotry, and you become the catalyst for the same problems that you complain about.