Are you claiming that the opponents of ID are all atheists? Is ID a religious topic?
ID isn't taught in science courses because (up to the current time), the proponents have been able to make a scientific case, not because of the religion (or lack therof) of its proponents.
IOW, because both science and the classroom are restricted to the boundary of materialism - metaphysical naturalism has an "unfair advantage" over all religions in publicly funded education. That is taking the view that atheism (metaphysical naturalism) is a religion and naturalism has the monopoly.
I didn't wish to derail this thread into a crevo debate. The poster asked for examples of unfair advantage, and that one came to mind.