An individual, often pretentious, that takes huge leaps of logic in order to claim an understanding of the real-world persona of someone they come in contact with through the internet. This is usually in an argument or debate, as internet psychologists usually love to think they are right about everything.
They have a tendency to point out things that people say and use them as evidence to "prove" they are a certain way in real life. Often, they are wrong, as they tend to stretch the truth of the facts they are given to fit a negative image of the person they are "evaluating" and just come across looking like complete tools.
Internet Psychologist: You're obviously someone ugly who can't get a girl and is trying to downplay it by saying you don't think this attractive girl is attractive.
Normal Person: Dude, all I said was that I personally am not into redheads. Stop being an internet psychologist.