Walk their dogs on there - you're not wrong. I've been over to that field to have a look and I can genuinely say I have never seen such a shit-infested piece of land. There is a pile of dog turd every few yards - it's absolutely disgusting and if people really let their kids play there, they ought not to. It should be sealed off on health grounds until the owners do the decent thing and pick up after their animals, as they would be expected to anywhere else.
That aside, if the residents want to have their say, that's only fair. But given the nature of the land at the moment, it's hard to see why a sensible development would be opposed.. and there could be a lot worse things than a football training ground on your doorstep, I'd have thought.
