Perhaps a better approach to take here, without directly challenging the
student's beliefs and yet allowing the 'ignorance' to show itself, would be
exactly to pursue the comment by asking the student to explain him/herself.
Yes, it is true that everyone is entitled to her/his own opinion, HOWEVER
that does not mean that everyone's opinion is right. Most of the world's
problems are based on incorrect opinions and fallacious beliefs. They DO
need to be challenged. This can be done, not by attacking the opinion
expressed (or, worse, the person expressing it), but by requiring the person
to substantiate, give the reasons behind, her/his statement.
In this case, the student stated that "Buddhism is devil worship". It is
simple enough to ask the student in what way is it devil worship. I would
not be surprised if the student knows absolutely nothing about Buddhism
except that it is not Christian. Ok, so if the student (or, his/her
parents) is using the definition that everything that is not Christian is
devil worship, then start to apply that definition and see where it leads:
are Jews devil worshippers; how about Muslims, Hindus, Taoists, etc.? Some
of them don't even HAVE a concept of "devil", so how can they worship it?
In any case, by doing it this way, you CAN challenge these fallacious
opinions without directly attacking the student, only the statement. Ask
the other students for their thoughts; if you have students with different
belief systems, you may have just allowed this student to insult them and
done nothing to defend THEIR beliefs.
Food for thought,