Since you child is in college, I will assume they are at least 18 or close to it.
Once someone is 18 they are a legal adult and there isnt much you can do. basically you can either kick them out and hope nothing goes wrong or at least let them stay at your house being non-jedemental and hope for the best and even if they are not relgious, at least they will be a mensch and a positive member of society