Well apparently 5 justices don't agree with you and like it or not they have more say than you.
Saying a prayer at the beginning of a governmental session is not supporting the establishment of a state religion.
An invocation at the start of a government session is not an indication of whether or not the representatives represent atheists. If government officials who subscribe to a given faith are unable to represent an atheist, keeping them from saying a prayer isn't going to change that fact.
Do atheists get their noses out of joint when someone says God Bless you after they sneeze? Sad to say, but I'm sure some do, particularly the ones who go apoplectic about "One Nation Under God" and Easter Egg Hunts.
A great many atheists seem to find a belief in God to be childish, and laugh at those who think that the favors of "an imaginary being" can be courted by a memo jumbo prayer. Suddenly the same practice can strip them of all rights?
I'm for religious freedom, and freedom from religion, but an opening prayer at a town counsel meeting just doesn't cross any serious line that I perceive.
I've disagreed with a number of SC rulings, but that counts for about as much as your disagreement with this one, and to me this one has very little actual impact at all.