This is what I see as constitutional. In 1776, this nation declared independence from British rule and developed a structure from which we derive our policies and decisions as a people. I would expect reasons to be provided that compelled the Supreme court to allow Louisiana to dissolve such ties that once bound them and has now enabled them to enact this law in their State. I'm sure there are many reasons.
At one time, and for over 200 years this freedom was honored in the schools and even our text books. Within the last 40 or so years, these freedoms were stripped from those who honor them. Going back to 1776 I learned something about the intent, so I expect a reason to be offered for the dissolution effort.
Edit: Also, what you seem to be missing in your suggestion is intellectual honesty, if only for the reason that only one state is allowing this while the other 49 have not yet made this type of effort as a majority per state, which means that Atheists are being honored in 49 of our 50 and our Christian base is being honored in 1 and every other religion is being honored in none.
Yet, you somehow deem it something selfish. I'm curious, would you prefer to live in a blue state with people who are more so likeminded than those in Louisiana or would you prefer to live in Louisiana where certain ties have been dissolved, enabling them to pass the law?