This is a screengrab of the wiki page covering the subject of fascism. (URL)
Note the word ‘Fascism’ in bold at the top, then the caption about Hitler and his little friend – both fascists.
These people and their politics were defeated at great cost.
So when someone talks about ‘anti-fa’ – they are literally talking about people who would stand against Hitler were he alive today.
Anti-fa are against fascism. You should be too.
Why? Because who the hell wants to live in a nightmarish, fear-fuelled dystopia.