Longbow - there's an order that a Chief constable can make that can be in effect for a set period of time, within a set area, that means people must uncover their face when asked to do so by cops - it is done for most football matches as far as I know, and for protests like the one on tonight's show. The reason for it is that it makes it easier to evidence when people do break the law with mob behaviour, as some people often do - usually people who have no affiliation to the cause being protested.
And the swearing issue - I agree, it looks very bad when a cop is swearing like they were. I fully understand it, and don't really disagree with it in some circumstances, and there are psychological reasons for it - I don't agree with arresting someone simply for swearing in those circumstances though.
TBH, from what I saw - about half the programme - the actions of the cops on the street were legal and correct, even if a couple of things didn't come across well on camera. The attitude of some of them in the post-incident interviews, however, was horrible IMO.