People confuse free speech with freedom to harass and driving people out. When 90 % of a site (as an example) are antisemitic rants and antisemitic memes Jews are actively driven out of the place. You actually make a place less free by allowing discrimatory content. People have to potentially hide their identity or have to endure constant hostility. In consequence you are removing their voices from the platform.

I guess most "people on the left" would agree that you can create such a platform for yourself and your buddies but do not call it "free speech" when in reality it just creates a venting platform for a certain type of people.