So climate protesters, LGBTQI+ protesters, refugee activists – all will be deeply passionate and frightened about very real and immediate harms.
By contrast Neo Nazis are there as much for the banter and the chance to intimidate those they define as weak. Both can be deployed to recruit new young men (and sycophantic women). There is no downside for them in these protests so far. A bit of a joke with some sympathetic police officers is a given. The jokes that make them easy work for the police act as recruitment.
Source: Why do police high five Neo-Nazis? – Pearls and Irritations