“To prevent doxastic closure it’s also important to read the work of noted apologists. The only two I’d suggest are Alvin Plantinga and William Lane Craig, though I’d urge you not to buy their books; their projects don’t need your support. If you must buy one of their books buy it used and support a local bookstore, this way the author doesn’t receive any royalties.” (Kindle Locations 3419-3421).
Remember the debate surrounding God's not Dead? I watched the movie and for the most part I didn't care for it, because most real atheist professors don't act like that atheist professor in the movie, who tries to get the class to sign an atheist statement in order to avoid dealing with the problem of God in the course. Even the most virulently anti-religious philosophy professors that I have encountered (and I have encountered a few) don't act like this, and it's a mistake to tell Christians that this is what they should expect in philosophy courses, including those taught by staunch atheists.
But people like Boghossian, I am afraid, make God is not Dead look realistic.
What is more, I do think the fictional professor in God is not Dead DOES violate the Establishment Clause, because he puts requirements for passing the course on believing students that he doesn't put on nonbelieving students.
Boghossian's course, I think, also violates the clause. That is because while he presents arguments against his own view, he provides a message in required course material that he, the professor, considers their arguments so unworthy of being taken seriously that students shouldn't provide royalties to the authors by buying their books. A teacher can say what he thinks in class so long as he also says there are intelligent people who think the opposite, and in the last analysis it is their responsibility to decide the issue for themselves.
As Randal Rauser says
If this really is his advice, then I must say it is absolutely terrible advice. Simply reading or listening to somebody you disagree with doesn’t prevent cognitive closure. The only way to do that is to read your opponents with charity. Needless to say, when you preface the advice to read somebody with the proviso that their works are so bad (and harmful) that you ought never pay money for the books if possible, you have undermined any hope in your reader of engaging their works with charity.
If you do this on the public dime, then you are shoving your religious views down the throats of your students, and the fact that atheism is not a religion in some other important sense does not exempt you from the force of the Establishment Clause.