I think a lot of it comes from arrogance and insecurity on the part of guitarists. You see it everywhere, not just guitar. How many tube amp aficionados look down on us for playing in the digital realm?
As a personal anecdote, around 1987-88 when I was 16, I had my first guitar teacher who was guiding me through the Mel Bay Primer. I told him I was into music like Maiden, Metallica, Black Sabbath, Guns N Roses. He would turn his nose up (he was a gospel/bluegrass player) and proclaim that all rock guitarists have 0 talent. He went on to say that its all one chord and that rock guitarists hide behind effects.
Of course, now I know that he simply wasn't paying attention. He never listened to rock beyond a surface level. When he heard Hendrix, all he did was listen to 5 seconds and all he heard was a wall of feedback. Of course he never heard the beauty in the chord/melody styles of Little Wing, Castles Made of Sand or the scorching blues of Red House. Is Yngwie one chord? Vinnie Moore? Ritchie Blackmore? Jimmy Page? Jeff Beck? Hell, this was the 80s, a time where the rock guitar talent level was being pushed into the stratosphere!
We all have personal biases at some level, but guitar is a wonderful hobby or profession to pick up no matter your skill level. To run down other players or their styles or gear is just pointless negativity.