Thanks for all the replies.
These guys don't seem to get that it's hazing. No matter how we try to explain it to them, they say that they don't see the problem with "harmless fun", "trust-building activities", and singing silly songs.
That's a really good point about it being a risk management issue.... Being a local music honorary, I doubt they ever really consider risk management, but if they're going to do things like this, they'd better start.