Why is the fact that they're "established" relevant to his opinion of their music, and how do you know that his dislike for Electric Wizard is founded solely upon his distaste for stoner doom?
I don't have a whole lot of experience with the genre, but I generally think that all of the stoner nonsense is fucking awful simply due to the constituent elements of the style. The overstated "dirtiness" of the bass-heavy fuzz sound; the aimless "psychedelic" composition style, the generally "positive" atmosphere and common "chill" themes (I'm fully aware this is a generalization and that EW deals with Lovecraft and other dark themes, but their presentation of said themes totally weak and uninspiring to me); it's faux-heaviness. Compared with the genuinely macabre nature of bands like Reverend Bizarre or the esoteric darkness of Pagan Altar's first album, the archetypal stoner band is just kiddie shit.
With that being said, there are plenty of great bands that utilize "stoner" elements (don't even try to call me on hypocrisy by mentioning Black Sabbath); but the style in its purest form is just fucking gay.