why is it ok for our sisters to borrow their brothers boxer shorts but if the brothers borrow their knickers we are perverts

LOL. I can see where you are coming from here. The reason why a person might want to 'borrow' a pair of knickers I can understand; I cannot relate, but I can understand that such men are out there and I wouldn't judge anyone. But I can see where it might appear there is a double standard somewhere, amidst what appears to be somewhat a conundrum :-)