I concur with all who are saying "Hey, there's a time and a place."
Seriously, nobody's saying "Good Morning" is a mortal sin, it's just inappropriate to a solemn occasion.
How would you judge the propriety of starting a U.S. Marine Corps Flag Ceremony with "Hi there, everybody"? or ending a funeral with "BUH-BY!!"?
i do not see those examples congruent to saying, "good morning..."