Well, depends what he means with "your"; OP specifically, or an arbitrary person? Because I think we are getting dangerously close to shooting down useful criticism and discussion for fear of hurting someones feelings. It's obviously insensitive to say that OP is a bad person because he is doing one-on-ones, but it should be totally acceptable to say "this is weird (from my perspective), I can see several issues with this, I wouldn't personally do this, but you-do-you", and often "(from my perspective)" and "but you-do-you" parts are implied; their absence shouldn't necessarily be taken as proof of mocking.
(Disclaimer: I have no opinion on partner one-on-ones.)
Weird is one of those truly terrible words that's used to control people who are different than us. It's nice for the person using it, since it doesn't actually mean anything and is thus impervious to arguments stronger than "nuh uh". It's almost never actually the right word, and should be avoided in favor of more descriptive language. In order for criticism to be constructive, it must be easily understandable by the person receiving it.
"Don't call people weird" seems like a good general principle (unless they self-identify as weird, in which case knock yourself out). I don't understand this compulsion to try and get people to fall in line and stop being weird.
The from-my-perspective and you-do-you parts are the most important parts, why would you leave them out? You're not in charge.
No. That's the whole point. If it works for them why would it be bad? Let's try and not shame people for having different approaches to things.