First, lose those "friends." Second, if this stuff bothers you (bad Asian representation on media, prostitution in Asian countries), do something about it. There are groups who work everyday trying to make changes to these things.
If your so called "friends" tried to annoy you and were making fun of the whole situation they're not your true friends. It sounds like they're just a bunch of senseless douche bags.
nothing to be ashamed about being asians man...its your friends that you should be ashamed off!!! Such friends you can do without.