Sure it is. If a majority of the people are a certain faith, Government should accomodate their customs and beliefs. Today government is down right hostile towards display of religious beliefs of the majority. If 90% of the community holds Christian beliefs, than it is appropriate for allow a prayer that reflects those beliefs.
The Constitution is about protecting the minority from the tyranny of the majority. That includes faiths. A faith cannot be promoted by the government just because it's the majority faith.
Perhaps you'd have no problem with a predominantly Muslim municipality promoting Islam as the "true faith" over Christianity?