If a handful of idiots attacked the police then by all means arrest and jail them - you won't hear a single complaint from me.
But feck some of the sanctimonious posts in this thread about respecting the Glazers private property. Running onto the pitch and waving the corner flag around hurts nobody, it's not like the megastore has been burned down or statues defaced.
Hashtags and grumbling online will never bother the glazers, but disrupting games? They will notice that.
Would be different if fans were travelling from all over the country to watch the game, the only people in the building are being paid to be there