To tell you the truth I know what you mean. I dye my hair a lot and sometimes I think the hair color that I pick actually affects the way people think about me. I mean I'm a natural dirty blonde/light brunnete but I've dyed my hair red,brunnette and many other colors and peoples way of perceiving me have change. (Now I'm brunette and loving it ;D)
I thinks it's because men prefer blondes, & since most people aren't naturally blond, it upsets some people. I personally couldn't care less, & will never dye my hair just to get a man (brunette as well).