I think it's mainly because Christianity tends to survive anyway. I mean I remember tarts and vicars parties from when I was a kid, people referring to godsquad etc and we all still went to church at Easter, for Christmas midnight mass etc. Christianity seems to be able to carry on, take in good part the humour (I've seen numerous cartoons with Jesus in them even in my DH very catholic home country). Also criticism numerous bands I know of have criticised Christianity in lyrics and as far as I know the church has not come after them with a big stick.
If the same was done in Islam I suspect it would be seen very differently.
For the record I think Louis Smith was probably more in the wrong for doing something silly whilst drunk. But having seen a great many people do vastly silly things whilst drunk and tell some hugely innapropriate jokes also, I think it was more down to the fact that he is a public figure and he made the mistake of doing it at an event which whilst private in the sense he was not there in a professional capacity, he was filmed.
There are a great many aspects of organised religion, including Islam I find totally ridiculous. However I don't get drunk, in public or private a great deal these days and I am not in any way high profile as he is.