Stereotyping... Why do we need it?

Okay so I just read a journal entry of someone who will remain nameless...
anywho they were talking about how they didn’t like a certain store cause it was "preppy." So I go on to read the comments that were left, and I was shocked that people started getting into a fight over what was said. They were all accusing each other of "stereotyping" each other. And I just have to say I was so confused.

I mean reall who cares who buys what at what stores. Why do people have to constantly
bash one another on where they shop? I mean sure each one had a right to say what they thought, and I’m not saying anyone was wrong or that they shouldn’t have said what they said.

I just don’t see the point in why people call someone "emo" if they shop at HotTopic or "preppy" if they shop at Hollister. I know personally it makes it hard for me to be myself and wear what I want with out being labeled/ stereotyped.

And I hate when people see u wearing skinny jeans and automatically think ur emo. or that u wear a polo your preppy. And I can understand if a person doesn’t want to shop at a store because there expensive or u just don’t like the clothes, I mean I do that.

Does it make me preppy if I like the way A&E jeans fit me? Does it make me emo if I like HotTopic’s hoddies? Hell no it doesn’t, it makes me. So basically what I’m trying to say is stereotyping is so retard so why do we need to do it?