Mod- I also think you’re being harsh. You’re allowed to question psak (though you still must follow it), and so far I haven’t heard a good answer to the question (and it’s one that’s been bothering me for a long time).
It seems the shape of the legs argument only applies to tight pants, but loose pants (and I think they are beginning to lose their status as beged ish) should be just as tzniyus as pants.
I heard people give the slippery slope argument (loose pants lead to tight pants), but according to that logic, women shouldn’t wear skirts because it may lead to tight or short skirts, they shouldn’t wear shirts because it mau lead to short sleeves or worse, maybe they shouldn’t leave the house at all! It’s all a slippery slope!