The point is that by better communicating God could have avoided much of the religious strife and tension in the world. This doesn't in any way disprove God. It only indicates that if he does (and he's all powerful) then he wants such strife and tension to exist, and you have to wonder why. Perhaps it serves some purpose I do not see?
If we all simply knew he existed and they he was as muslims (or whichever religion is right) envision him instead of how pagans or christians (or whoever is wrong) envision him, then the only "test" would be wether or not you choose to follow and obey his commands, instead of wether or not you can figure out the religion puzzle. Making us know what he wishes us to know would not take away free will. People would still be free to reject him and rebel against him (which is what I am often told is what I do anyway - but one can't rejecthttp://www.islamicboard.com/newreply.php?do=newreply&p=1389966 or rebel against something that doesn't exist).
It is a similar question that I have pondered on Christian forums. Are people who don't believe in God capable of blasphemy?