Well, I wish I had this problem - being able to fly business class regularly and look that young

I think we all have that generalization and sizing-up people tendency - it is human nature. In the service industry, I guess it might be worse - they have a huge sample size and probably size people up out of habit. The trick of course is to not treat customers differently based on our generalization, opinions, past experiences and prejudices.

As I mentioned in the other thread Treated Differently as an Asian Passenger , UA has an internal Diversity group to help with this kind of thing.

All that said, the only time I have personally experienced out right rudeness on UA TPAC J from an FA was an older SFO-based Asian FA. I wonder if OP had her.

When this kind of thing happens, it is hard to prove. On one hand, it does not help to think this way and one should move on. On the other hand, if people do report this kind of thing and UA keeps track of it, maybe they can see patterns.