Because an unlimited, endless stream of pro-Christian (whatever that means) statements by the Chief Justice of Alabama, or by the President of the United States, is not an Act of Congress and does not constitute an establishment of religion.
The vast majority of Americans are Christians, and are called to vocally and publically profess their faith and attempt to convert others.
This free exercise of religion is constitutionally protected, and establishes nothing.
My statement was used to show that he intended to literally "practice what he preached," which is a no-no when it comes to a government official establishing religious principles under color of law.
Further, as for the "a judge is not Congress" arguments I've been seeing around here, what legislative body do you think provides judges (and other government officials) with the power to be judges and oversight and control for same?