I think this magazine cover has accomplished exactly what it set it out to do: create controversial art. If post-modern art isn't stirring up opinions, then it's not doing its job. In the case of Playboy, as is the case with many of its past issues, controversy creates sales. Another perfect example is this one, where Lil Kim used the politicization of Islam to make a juicy front cover that caused a lot of controversy. No one rioted over it, but it was still taken seriously by people of the Muslim faith.
It's definitely insensitive to create front covers that mix sex with religion, but that is partly the message. They are two elements that traditionally don't belong together, which is precisely why it gets used and why it succeeds in irritating people. Playboy is an industry that thrives on what religious would call blasphemy or hedonism, thus it's going to have imagery that the religious won't agree with.
The religious people who become annoyed about this become part of the viral marketing that gets more copies sold. For every person who is shouting about how inappropriate it is, there is going to be another person who is given the idea to go buy a copy!