Not sure what gives you the right to tell people what they can or cant discuss. Do you go down the pub and butt into people's conversations and tell them what they're allowed to talk about?
As stated, if you don't like the post, don't read it. It's not hard is it? As has been shown, people discussing it literally has no effect upon you other than forcing you to scroll past it. Not sure why you feel the authority to order people to stop doing something thats of very little concern to you at all that they are clearly 'enjoying.
If every post started to become non football then you may have a point, but there's plenty of football discussion on here also alongside the seemingly endless brexit and tommy Robinson posts.