I think the underlying reason for "improving attractiveness is evil" is largely a mixture of egalitarianism and a disconnect from reality. The idea is:

'I want to believe that everyone is attractive, therefore anyone who tries to become more attractive is evil. Do they think they're better than us?'

Now, admittedly, if attractiveness is a purely positional good, then this would make sense. But I don't think this is the case.

Similarly, I've heard the idea that universities giving female students advice on personal safety is evil, because in a perfect world no-one would commit violent crime. The fact that we don't live in a perfect world does not seem to have occurred to them.

I don't see a reason not to leave them behind, all else equal.

To a large extent I already have, moving away from them a few years ago. Not that I don't enjoy their company, but they are rather entropic people.

A second possibility is simply adopting a strong mental attitude of independence. Since reading about cogsci and how the mind automatically accepts everything it hears without making a concious effort to question its veracity, I've begun consciously marking opinions I hear as "someone else's opinion".

I think we can find better peer groups which engender habits of expressing a desire for self-improvement better, and peer groups which won't punish individuals when desires are expressed.

Well, this is strongly characteristic of LW. I have attended a meetup where we did assertiveness training, which I would think is far more helpful than advice about 'just be yourself'.

I wonder what other ways there are to find more positive peer groups? Offline, I have found martial arts people (or, other sports people) are a good start. Online, I wonder if other groups similar to LW have organised meatspace meetups - I used to lurk around many H+ organisations, but not for a while.

I looked at r/malefashionadvice, and it seems a little too 'what is in this season'. I'd rather have clothes that are timeless, rather then having to reappraise my wardrobe every year. Still, I think this:

becoming "a gentleman" rather than a "pick-up artist"

Seems a good idea.

It's an unfortunate trade-off for bad credence calibration. I'm not sure it's a trade-off worth undoing, though.

People have raised the possibility of doublethink wrt this sort of thing - simultaneously believing something with absolute certainty for the sake of social confidence or psychosomatic effects, while also having accurate, calibrated beliefs where necessary. I wonder if anyone has actually got that to work.