If you say that metrosexuals are metrosexual (duh) it’s not stereotyping, however
If you say that Irani men are metrosexual, because the few that you have encountered in your life were metrosexual, it’s stereotyping.
By looks alone, metrosexual men could be stereotyped as gay men. So you do the math and you’ll know why some people might think that they are gay…