I think Antifa actually started in the UK even before the Nazi’s. Eh actually not but they did fight against fascists in the UK as early as 1930.
The reason why we need antifa and why it’s hated by the mainstream is because the establishment is notoriously bad at stopping fascism. There is a long history of it. So besides liberal antifa that uses legal means like suing the KKK out of existence, the autonomous antifa is actually needed for the continued working of our democracy.