To most JWs it's simply common sense and part of their beliefs
This is simply not true. I had several very active JWs that are not aware of my beliefs about the organization tell me (somewhat sheepishly and in hushed tones) that they were personally and privately disturbed by Anthony Morris' comments about metrosexual dress, yoga pants and colored socks.
And when people start posting images of people in tight pants as has happened umpteen times then it really makes their point for them - they are immodest and out of place for a christian preaching setting.
Who posted pictures of people in tight pants while preaching?
I posted a video (which I noticed you removed) of women wearing yoga pants while exercising or doing other ordinary, every day activities. None of them were engaged in the "Door-to-door ministry."
saying that gay people can be identified by their clothing shows an ignorance and willingness to accept caricature stereotypes
You are right, except we here didn't make that assumption. This is the assumption implicit in the WT letter.
THAT is the problem. You got it!