zahavasdad,
While they might about beliefs in general they usually wont single you out. They might say “Judaism is stupid” but they usually wont say “Your Beliefs in judaism is stupid”
The distinction between general comments and singling out a student gets pretty blurry when the comment is made seemingly at random (unrelated to the course material), with an obvious member of the faith or ethnic group sitting in the front row. I’d imagine that mik5 felt quite singled out.