If the priest said F God and meant it I would say yes. However, we don’t know how he said it, the reason for saying it. We do not want to take the expression out of context or misread the intention. How did it sound to you? Were you shocked? At the least I would say that it would be in poor taste. We were not there to hear it said so it would be hard to judge the reasons of ‘why.’ Cussing is in poor taste. Cursing something or someone is blasphemy. Even exclaiming OMG-Oh My God! should not be used to express one’s self. Do not take the Lord’s name in vein. Think about it… Peace.