polly I wasn't involved in that conversation but I don't think anyone was being aggressive toward you - you were the one who brought in words like 'slut' - that word is so derogatory, has nothing to do with the length of someone's skirt, and is a word I think no woman should ever use to describe another woman because it is a misogynist and horrible word. I think that's the point people got really annoyed with you - not for your opinion. Nobody else was using language like that, which is off topic anyway.
I think people think you are showing your age because you see 39 as old. As most of the threads suggest, it really all depends on figure, body shape, confidence in the dress, cut of the dress, and so on - as it does for anybody at any age. My mum is 50, she's a size 10, she's stunningly beautiful (it's always her and never me that gets chatted up when we're out together, even though I'm 22 years younger than her!), and though she probably wouldn't wear a miniskirt these days she would certainly wear a sexy midthigh dress and look bloody gorgeous in it. Haven't you seen Sex and the City? Those women are in their late 40s and look fantastic. Tess Daly is 41 and she was on Strictly Come Dancing last night in a beautiful cleavage-revealing dress and looked stunning. Jennifer Aniston is over 40. A midthigh dress looks great on a woman with good legs, regardless of her age.