I've visited dozens of mosques over the years (eg the Blue Mosque in Istanbul, the huge mosque at Kairouan in Tunisia and the one at the University in Norwich) and have always been given a veil to cover my hair. I always wore a full-length skirt and a loose top with sleeves. (and slipped my shoes off at the door)
Didn't mind in the least, it's their religion and their dress code.

As a child I was often taken to Catholic Mass with my RC cousin. She always wore a lovely lace mantilla, and lent me one, which I thought was delightful. Again, it seemed quite natural as that was the norm in those days.

Later in life, I sometimes attended Mass at a Catholic church in Norwich, and was touched to see a large family of Travellers seated in a pew. They were very poorly dressed, muddy jeans, ragged dirty T shirts, scruffy shoes, but they were welcomed and embraced by the priest and many of the congregation. That was lovely too.

I reckon if one goes out to, say, a posh restaurant, or a job interview or even as a guest to a wedding, there is usually a dress code.

I wouldn't dream of visiting my African Muslim family without having my legs entirely covered in a long skirt. One just does NOT show one's legs there!

I think the 'touching up little boys' is a separate issue.