Asking Gilly about his hate towards Floyds is somewhat like dancing about architecture. As in - he knows it is something of universal appeal across many generations, he knows it sold better than any band in British history (including Beatles, but that's more due to overall inflation) and their legacy is more of an axiom, than a topic for discussion. He knows all these things. But the fact he knows it just annoys him even more, so he will add "there is no spoon" wherever and whenever he can in hope the lie will one day turn true. I guess we all have that kind of feeling of deep hatred towards someone or something - for me it's the fascist mayor of London - Ken Livingstone. If it was up to me I would have him flown in a trunk to Venezuela, released on random street and then all traces of him, his life and his bloodline removed from records. His legacy vanished, memory of him gone. The good thing is - I know Ken Livingstone will be gone come next elections, and if not, someone surely will have him executed or imprisoned for life sooner or later, whereas Gilly faces Pink Floyd haunting him for the rest of his life. 
