I don't think its above criticism as much as its influence in society has made it risky to criticize. Until recently non-believers (heretics, infidels etc.) have been careful to only criticize outside of the public eye. Even today in the workplace or social situations there's little incentive to criticize religion in case one finds oneself isolated from the majority and a pariah in an environment where one needs to see people regularly. The reward is just not worth the risk. That's why, as Whoaccio mentioned, religious people tend to get together and discuss their thing while the non-religious do the same. However, the latter group usually has to make greater and more careful efforts when doing so.
There's still no way an atheist could become president and I have a feeling any future Canadian Prime Minister would also have a hard time overcoming this obstacle even though the vitriol would be less pronounced up here. Ironically, even as Christianity is taking a hit in Canada in modern times through moderating influences and diminishing numbers the increase of observant immigrants is ensuring religion retains its power though not its exclusivism. I don't think things will change too quickly as far as religion being above criticism is concerned.
I'll add a plug for Maher's film as well. Aside from a few odd ideas about health care Bill Maher is a sharp wit and quite intelligent on the big issues in general and Religulous is worth seeing.
The rise of the Internet as well as bold people such as Richard Dawkins has made a slight impact but its difficult when you're up against thousands of years of belief (even though many belief systems that were quite significant for their times have already risen and fallen, so nobody seem to respect the Sumerian gods, Egyptian gods or Roman gods simply because the followers have disappeared--so much for god being eternal). Would anyone get offended by a bus that said: "There's probably no Zeus, now stop worrying and enjoy your life."