I can only answer this in simple terms, neither of us would go into a church or cathedral and scrawl graffiti (even Banksy would n't) on the wall or knock bits of stone out to take home as a souvenir, we respect the edifice though not the religion that it is dedicated too.
Rhiannon has covered the subject about respect, it is the social pact we make with the people around us to behave in a courteous fashion. That which is wrong in religion, and there is so much of course, we can speak out against.