How do I tell him?

Sometimes we float on a cloud of blissful ignorance. Most of us are afflicted by some form of myopia.  Yet ignorance is no excuse in the eyes of the law. Just try to explain to a police officer that you didn't know about a speed limit.

OK, at most milongas the organisers won't impose a fine for anti-social behaviour, but most socially aware adults would certainly disapprove of those who make us feel uncomfortable.There tends to be a fairly common understanding in social groups about these matters. Lacking the courage to confront a person directly, people often grumble about the offending behaviour amongst themselves.

Are any of these "oversights" familiar?
> Too busy to take a quick shower before heading to the milonga?  No problems, just spray on some deodorant or cologne.
> No time to iron a clean shirt?  Easy, a T-shirt will do.
> Forgot to brush your teeth?  Just pop some breath mints.

Sorry, that's simply not good enough in this intimate dance. Your dance partners won't enjoy being subjected to that, despite your superb dancing skills! Most of them will simply be too polite to say anything to you, but that won't stop them from thinking it and having second thoughts about dancing with you!

On the other hand, those ladies and gentlemen who make an effort are considerate to those they dance with.  Looking and feeling good also helps boost the confidence.  And in this dance, we can all do with that!

PP