How terribly sad – you are missing out on so much experience. Stereotyping people is worse than stereotyping animals. Anyone who studies animals for even a moment will see that each has its own personality, strengths and weaknesses. Humans are so much more complex.
By stereotyping a person you do not get to see the depths below the surface and so miss out on so many things and knowledge that person may be able to offer you.
One example – by stereotyping – Sam Fox in the UK was judged and disregarded as simply a blond Essex bimbo who was happy to appear naked for the press. She later used her earning to start a very successful business and proved herself a very capable business woman.