Forum:Rule issues

Well here goes my friend says that we can attack our own monster like his luster dragon can attack his ow mask dragon im trying to tell him its impossible but only thing he answer is that im a girl and he wont obey me since im a girl and he is sure he is right can someone tell me if we can realy attack our own monster or not??? 2 of my friends says we can but that makes no sense so please answer fast =/

ShadowTina