I simply think there is nothing for the club to "sign up" to in this case, particularly if this request is all about a particular politician's bandwagon. Leave it to individuals to speak for themselves and do as they see appropriate.
You see, that's where my issue lies. Why should clubs have to "sign up" to it? Stuff like this is a personal choice, not a decision taken by the Football League or the FA or whoever. I know certain messages can't be displayed in football stadiums, and probably with good reason, but I still don't...
I'd have thought the decision to take a flag of this nature (or anything similar) into a ground would be a personal decision for that individual or group of fans. Somehow, it would lessen the gesture for me if the likes of Yvette Cooper are jumping on the bandwagon & using it to make some sort...