Well I watched it and I didn't hate it! I DO hate all the songs but it's a solid movie. Very artful. I can see why people may have been disappointed coming out of the cinema watching it but I think it's highly underrated.
I think what Gunn was trying to say is that if you don't agree with his canon he doesn't care because it's all fiction anyway. However, he is trying to create a distinct canon for the DCU.