I just think your narrative about what happened at the stadium is just entirely wrong. Fans breaking in - that was organised. Pissing around on the pitch? Aaaah no, a boy kicked a ball into a net on a football pitch! Send in the SAS! I actually think that was a lovely example of uninhibited footballing joy, and I don't get why anyone would object to that. Damaging equipment?? I don't think anyone in the world will lose any sleep over that, and I don't think it undermines the protest in any way.
The biggest deal of the things you've said is the violence between fans and police officers. But even here, the United account (never contradicted by police reports) says that no violence was directed towards police before 4pm, when police started trying to disperse the protest. United fans say that the violence was instigated by police. I believe that, having been in other protests over the last few years where police suddenly began acting aggressively. Not to condone the violence that did happen, on both sides, but you seem to be victimising the police and castigating United fans, which is not balanced - especially as it should be the police's job to protect people from violence.
Have you ever tried to organise a protest? Believe me, this protest was well organised and really impressive in many ways. It achieved its goals, expressed its aims clearly and warned of what could happen if its aims are not addressed. 10 people being aggressive in a protest of 10000 does not mean the protest was not well organised - to me it means the opposite.
(I'm out of posts for today, so will have to reply tomorrow)