As for men being shirtless, I am one person on "the left" that wants to see more of it, not less. I think men that spend so much time and energy to look like Adonises should take their shirts off and show off what they have. It's good for community morale to see healthy men .
As for women, breasts are normal and natural, and there's nothing wrong in my opinion with a topless woman on a hot day hiking up a hill, or on a beach trying to stay cool. It's just fine to me.
but have respect for families with kids though - I think if I had a child I would not mind them seeing a topless person on a hot summer day, but there's others that would not want the children to see that due to them feeling its "improper" or "inappropriate", so there should be a level of respect for those that don't want to see you without the right amount of clothing.
I feel as a society we've become so much more casual. In the year 1950, I bet it was very odd to see a guy jogging around a crowded neighborhood without a shirt. Today, in the summer, you see it. It's a different time.
Actually tend to agree with your first point; I think the expectation to be shirtless in a pool or on a beach has helped motivated a lot of men to work out and stay healthier. I've noticed in NYC an increasingly large subset of (mostly fit) men who make shirtless part of their casual style if they're just going out to the park or something. This is a bold take, but unless a place is like a fancy restaurant or somewhere where certain formalities are expected, "no shirt no service" policies should largely be abolished. I don't see a problem with a shirtless guy walking into Starbucks to buy a coffee.
One thing I will say is there is an issue with unrealistic body standards for men, but I think that's more of a problem with social media rather than too many men being shirtless irl.