The “alt-left” label is a bit eye roll inducing to me because it seems completely synthesized as some tit-for-tat term for political argument and slurring. Whereas alt-right originated from reactionaries as a more of a self descriptive term (for some reason I thought it was Steve Bannon who first coined it but Wikipedia says it originated with Richard Spencer). Admittedly though it got appropriated as another boring catch-all slur.