I read a similar presumption that people shouldn’t wear denim because they claimed that in England, apparently only the low-class, unrefined dregs of the working-class society wear it. I’ve never been to the UK, but I’m pretty sure that denim doesn’t necessarily connote such traits. And wearing denim doesn’t necessarily connote support of the Zionists either.
Don’t get me wrong, I don’t care for leather accents, but if these girls are not wearing leather in a provocative or overly abnormal, eye-catching way on otherwise unquestionably tznius garments, then I really don’t see what’s wrong with it.