I would have asked him to call the Captain. If it was an American line (or to/from American waters) - you are perfectly correct in that they cannot discriminate. Whether some would rather see the legs of women rather than yours is not relevant.

I would have stood my ground, let him "escort me out" with a picture of the lounge and then filed against him.

I have a friend on the Cunard where similar happened and he came back wearing his kilt.

I have done this in situation "shoes and socks required" where I wear sandals. The women are obviously not wearing hose or stockings and have open toe shoes. I have a pedicure every week and my nails look better than most women. I threatened to publish the photos and video and got a free trip from the line.

My "men only" health club in Chicago was forced to allow women and now I note there are several "women only". We have had the DA threaten prosecution.