That which is different and unexpected stands out. The voice one doesn't expect to hear in a room seems loudest. The people one doesn't expect to speak seem to dominate the conversation out of proportion with their actual words spoken.
I have even seen people claim "sex workers run Tumblr."
But that's only part of it.
Insecurity and anxiety and other things can lend greater weight to voices that seem to be saying you're wrong.
Personally, I try to remember that Twitter I See is not Twitter but a slightly random and very arbitrary subset of it.
I try to reflect more than I react.
And one person cannot self-improve themselves into better community discourse.