Don't get me wrong, I agree, but the fact of the matter is that football is a seated spectator sport these days.
When people buy a ticket for a seat they are perfectly entitled to sit on their arses and watch the match however they see fit. The singing section at the final wasn't advertised as such to the general public, was it?
If some Joe off the street went in to buy a ticket for him and his grandson was he told by the staff that this section was a singing section and most likely would involve people standing for a good chunk of the game?