1/ I know because I know how the strictures of Islamic society work in relation to the male domination of women. Did you not notice the way that the Taliban and ISIS on taking anywhere over immediately insist on extreme clothing restrictions and an end to education for women? Do you imagine that's just a coincidence or do you maybe think it might be part of a pattern of extreme systematic social control of men over women within Islam - of which ridiculous garb like this is just one manifestation? Any woman telling you that she's wearing this because she wants to is simply a victim of the extreme social and religious conditioning of her culture. To find out how 'free her choice was, ask her how her menfolk would react if she turned up to the beach in a bikini.
2/ Nothing silly about it. These garments are simply an attempt to normalise a backwards thread of Islamic thought whose roots are exactly the same as those that currently feed global Islamic terrorism. Making that link may make you uncomfortable, but it's true.