Assalamu'alaikum,
IMO, I think it's actually really important we learn about other religions (and respect it too) so that we can rebuke what they say if a question ever comes our way about Islam with knowledge of where they're coming from. We need to know what they believe in and why they think this and that and what Islam says about that particular topic. Learning about other religions provides us with the essential knowledge that is needed to debate and discuss issues with others.
For example, this might be quite a simple situation, but its still important to understand: Christmas, to be able to someone especially children why we don't celebrate it and how our beliefs differ with regards to Muslims belief that Jesus AS is the messenger of Allah swt, not His son etc we need to have known why Christians celebrate Christmas, what's the story behind it etc...
However, I agree with Brother Rafeeq, you need to be quite careful with younger people..