Except when it is. Given sufficient downvotes, a post will fade to the same color as the background, making it easy to scroll past and not see it. Whether you want to admit it or not, brigading happens here too, and once in a while a perfectly valid, thoughtful, and reasoned response is silenced because it doesn't fit in with the group mentality here.
The only solution for this issue would be for everyone to adopt a personal policy of only downvoting trolls, intentionally misleading comments, off topic comments, spam, and "me too!" style comments that don't contribute to the discussion. Unfortunately we're only human, and instead of rebutting a comment one disagrees with, many of the users here take the lazy path and downvote. There's no easy fix for that, so the brigading continues, as does the censorship of valid but controversial ideas.
As for the topic at hand; while I agree with most people that the word "retard" is offensive and derogatory towards a specific group of people, I find it hilarious that its use is being questioned by people running a site/service named after an equally offensive and derogatory word.