Is it bad that I agree with this?

[Alex]

Originally Posted by Capt Jack

but rarely does anyone considered 'over X BMI number' do so intentionally

I think it is safe to say that most (not all, but most) people over X BMI do so intentionally. They may not like that it is the result (or prefer it over choosing another BMI) of what they choose to do but it is still voluntary.

If someone wants to starve themselves and someone else thinks this makes a dress look best then I don't see why it is anybody else's place to interfere with that.

Since the goal is to require "healthy body images" I would assume that this implies a cap on BMI as well (though I doubt any designers were approaching it). I don't think turning away a BMI of 29 (or whatever the top of healthy is) because "girls emulate what they see and it would encourage them to put on weight to a level known to increase the chances of diabetes and heart disease" would fly very well.