Its very easy to conflate 2 very complex issues here.
Booing a minute's silence is always going to upset the overwhelming majority of people - and thats the risk with having them really. Remembrance commemorations are more important in the UK than anywhere on earth in my experience.
BUT, Irish nationalists see the British as being an occupying force, literally. For many in NI (and Celtic identify themselves in that way, as a "Celtic" club), the British are the enemy.
For some people, asking them to respect that minute's silence is like asking Americans to respect an act remembering the Taliban's fallen few.
Its THAT emotive. I dont agree with them, but I can see how and why it has evolved that way.