Well, are people nice to each other because they want it or because it's in the CoC? I'd rather deal with somebody that doesn't like me upfront rather than mask the quarrel with policies.
If you don't pay attention to the erosion of community occurring under such projects, then that's your own ignorance, not the basis of an argument. You can reframe the discussion in terms of "being nice to eachother", and your opposition as "in favour of not being nice to eachother" in turn, but that doesn't mean that's the actual dichotomy.
"Be nice to each other."
Unless you're CoC is targeted toward a hypersensitive kindergarten, that language has no place. You need to realise that it's extremely unprofessional, infantilising, and patronising. You're going to alienate a lot of talented people who have no patience for that rubbish. You're going to be on the fast track to a mess where blue-haired amateurs are feverishly reminding everyone of their pronouns rather than having a group of grounded, professional adults getting things done.
People "feverishly reminding everyone of their pronouns" are not being polite, professional, or nice.
Getting worked up over occasional polite requests about pronouns is not polite, professional or nice either.
Because they are professionals, and your new look or whatever else has nothing to do with the job that needs to be done.
I'd say the same about your behavior. If you keep doing the job and politely point out that you'd like to be called Sally, that's fine. If it interferes with you doing your job, then that's a problem.
Oh, let me just pull up all the peer-reviewed studies that people have done comparing the impact of CoCs versus... oh wait, that obviously doesn't exist. Do you have "some evidence" you'd like to share? I'm not really sure what you are looking for here.
> What on earth about being nice to each other is overbearing
This is such an absurd motte-and-bailey. Are you really trying to sell us on the idea that the 5000+ word "contributor covenant" is nothing more than "be nice to each other"?
What on earth about being nice to each other is overbearing? Which bit of the contributor covenant do you find particularly overbearing?