Just to let you know, I used to work for JAL, and the japanese AND western crew would NOT find these comments funny at all.
I don't know about your friends, but if the comments were about an asian or black person it would not be funny, so why is it because it's about Japanese? As a british/asian woman myself I know from experience this is where ignorance about other cultures starts.
And remebember, if you want to be cabin crew, you will be working with many people from other races and cultures, be a bit more smart will you!
And no I will not get over it.