It would have been your perogative to yell - "IS THAT HOW YOU TREAT A CUSTOMER WHO IS ABOUT TO BUY A DRESS?"
You did nothing wrong. If I were in your shoes I might have yelled back at the manager.
I would have told the SA straight up that I was a man, and I would like to try on some women's clothing. The SA could have had the option of leading me to a men's changing room. After that was done, if the manager came by and conducted herself as described above the whole store would have heard my response.
Yes, I think you need to sue for emotional pain and suffering, and damages.