As a committed Catholic, I am offended by this. Furthermore, the reactions that say "oh it's just art" and "we don't want to censor creativity" or whatever, are typical of our modern day flip flop of values that says good is bad and bad is good. I am not surprised.
My best response to this kind of situation is to say, fine, maybe in our warped modern day world, you have the right to display any kind of offensive trash you please, but I have the right to vote with my feet, and I will never never never ever set foot in your establishment again. I would write them a letter saying just that. If I happened to be a benefactor of said establishment, I would cease supporting them.
When Christians (and any other group) are offended, they should 1 - be vocal about their offence, and 2 - boycott the offending party. Let's see how long the principle of freedom of expression exceeds the principle of running a long term profitable venture.
imo