Because I'm being asked to pity them? Yes, the comments are nominally phrased as, "Oh, here is a possible case of people being biased even when it would pay not to be", but the obvious tone is, "poor women, no one will make clothes for them even when there's money to be made".

That's a plausible motivation. But use of the term "pity party" could have implied that you were trivializing the concerns of fat women, which is probably why you got downvoted. Really, I think you were just trying to add another, similar concern: people with wide feet. If you'd just said "people with wide feet have a similar problem," I don't think you would have gotten a negative reaction.

And frankly, when the asymmetic bra issue came up, I got pretty scared. Some of the commenters -- and I'm not going to single anyone out -- sound like really angry people in general and I fear that being around them would make their rage spill on to me.

I don't share this perception.

Also, are you going to take back your pretense of ignorance about shoe prejudice?

"Pretense of ignorance" sounds like you are making an accusation of bad faith.

I hate watching you make good points that get downvoted because of the emotional or interpersonal content in them.

Rather than try to fix everyone's thought processes on the spot, I prefer to instead demonstrate a rational thought process myself (with an interpersonally likable communication stye), in hopes that people will want to embody or engage with this sort of thought process. Pull, rather than push.