Secondly, the clothes fit and they're clean.
Black blocs usually include a fair percentage of squatters, as well as metalheads and other reprobates. Some people clean their clothes, others live with parents or partners who do that for them, but you're never going to get everyone turning up in crisp stuff smelling like it came out of the dryer.
Likewise, a lot of anarchists wear second-hand clothing, either passed around via free shops or by hand, or from charity shops. Clothes stretch over time, and human bodies change. Ill-fitting black hoodies are practically de rigeur. This is reflected in the appearance of the black bloc.
These fash, though? All their stuff fits perfectly. Their patches are all well-sewn. Look at them. Derek Guy might criticise the sizing or the cut, but I am not Derek Guy. To me, this is well-kept clothing carefully sized and washed, and possibly new. This is clothing-as-class-signifier.
What you are seeing is not just a display of racial supremacy, but of class supremacy.