What is the adjective to describe someone who views or represents someone/something as a stereotype?
Solution 1:
I believe that the word prejudiced might help you, in the sense that somebody can have (sometimes false) preconceptions about others. Else, you could describe somebody as 'holding many preconceptions about others'.
There is also the word bigot, used to describe somebody who doesn't listen to others and is often set in their views. The only issue with this, is that somebody who stereotypes seems to want to be described by a "softer" word.