John Mayer is a douchebag ... in fact, he's "King Douche" ... this according to country music bigshot Shooter Jennings -- the son of country legend Waylon Jennings.
Shooter -- a powerful country music DJ -- just went after Mayer on Twitter ... saying, "I love how the 'neil young of our generation' self-naming king douche grows his hair out + buys a place in Montana just to do [Rolling Stone] article."
Shooter continues, "Claims he's 'done w hollywood game' and has 'roots' and then immediately cuts hair, goes back to hollywood clubs + starts banging Katy Perry."
The attack continues ... "And don't anybody say he's a great guitar player. Gary Clark Jr & [Lukas Nelson] wipes their asses with this dude."
It's unclear if Shooter has any personal beef with Mayer ... or if he just felt like unloading for the hell of it.
RIPPED By Shooter Jennings
You're a Total 'Douche'
10/31/2012 2:28 PM PDT BY TMZ STAFF
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