The reactions here are pretty much over the top, and this is a conservative and definite non-fan of Obama saying so. Please read up on the history of the oath if you believe it to be a big deal. Here's a good place to start:
You will find that Ronald Reagan was one of four other past presidents who also took the oath in private and on a Sunday. If you still want to make a big stink about it, go ahead, but I think we have much bigger fish to fry. Personally, I would like to see Americans come together and figure out how the tradition of political discourse can be raised from the dead.