This is not to excuse poor treatment. I wouldnt accept it and dont think anyone else should. Just some thoughts on why it might be.

Several times I've heard FA's talking to each other. From my informal unscientific
easedropping:

FA's don't like extra work(most of us don't)
so they like people who travel alot, they are less work, they know where to go, they know the ropes. The conventional wisdom(whatever good it is) is that many women are inexperienced and thus more work).

This may have been true 15 or 20 years ago,
but old impressions die hard.

As for dressing casually, well I fly that way almost half the time and I havent noticed a difference in treatment.

It would be interesting to video and study FA/passenger. All the combinations with respect to gender to see if there is a pattern.

What about Male FAs. Do they give better service to female passengers. Does sexual
orientation come into play?

Freud could have a field-day with this topic.

On a serious note, maybe its up to us guys
to take action here. Show the world the Chivalry isnt dead.

Guys, Next time you see a woman passenger near you getting sub standard service in relation to yourself say something to the FA. Of course that raises the issue. Would that be viewed as patronizing or perhaps a lame pickup attempt? Would the woman passenger be insulted?

There are so many possible issues, are women
FA's threatened by women first class passengers? Does a sucessful business woman make them feel.... I think I better stop.