Antifa is a political group full of militantly liberal individuals who all stand against everything that fascism stands for. They are extremely left leaning, and they support tolerance. Their version of tolerance is tolerating things that only they approve of, and those that do not agree should be eliminated from Earth.
They only believe in free speech when it agrees with their ideology. The Antifa will use violence and intimidation to further their message. While the group is specifically against fascism, they hold many of the core values that Nazi Germany did, which is quite ironic. Of course, brain power was never the strongest trait of these individuals. In any side, it is never a good thing to go to an extreme. Extremism hurts a cause rather than helps it.
Regardless, the other side is no better. At this point it has become a peeing contest between both sides while the more reasonable people stay home.