How does one define OBSCENITY? That's the slippery slope. A government official can define those terms on his whim and make laws accordingly, thereby limiting journalistic and artistic expression. He can call any column or article criticizing him or exposing his misdeeds as "obscene".
It has been defined by and explained in foreign and local jurisprudence. If "whim" will be the basis for the definition, such ordinance will easily be declared by the courts as invalid. The last sentence above is stretching the argument too much.
Even providing that the term is hard to define, still, the decision to support such an ordinance is not bereft of basis, that is - legally and morally. Also, even if there are priests that are rapist or otherwise immoral, the Catholic Church is still not guilty of double standard if it decided to back-up the said ordinance.