Why are “anti-Fascists” attacking Trump supporters?
Ask them.
Until I hear their leadership condemn the violence, it is reasonable to assume that they support it.
They don't know and don't care. They are weaponized feral youth, being told and taught that they are Good People for beating women and the elderly, while wearing masks, and that Virtue Signaling is all they want, need or crave... but they likely are being paid for their services as well. The fact that neither Trump nor anyone else advocates for Fascism is irrelevant. The fact that they use Fascist violence and terror tactics to enforce their ideology, while calling it anti-fa, is ironic, but the irony is lost on them.
Because they are actually fascists, but can’t see the irony.
Because they are actually facist that call themselves something else for better news coverage.