Firstly the politicians have been imprisioned without trial and for political reasons. Secondly London has never been independent of the UK so the comparison doesn't work.
As far as I'm aware the yellow ribbon is supporting elected politicians who haven't dabbled in terrorism in an attempt to progress their ends. Something Irish along the lines you suggest would be supporting terrorists / those that support terrorism.
Personally I think it's pretty pathetic from the FA but nothing every surprises me from them. It's also rather strange they don't allow it but UEFA do !