Word for being guilty of stereotyping

The other day a friend of mine said something that i considered to make him guilty of stereotyping. I was lost for a word to explain that to him so I said 'That was very stereoptypical of you.' we both knew this was wrong but couldn't think of a way to describe it other than saying he was 'being prejudice'. Could someone please tell me if there is a variation of the word stereotype that would have been applicable?

Thanks!