One of Garcia's most notorious dislikes was toward fellow 1960s psychedelic pioneers The Doors.

Chalk it up to an in-state rivalry or perhaps a lack of shared ideals, but Garcia wasn't fond of Jim Morrison and the rest of the band.

Although the Dead would often cross paths with The Doors, including running into the post-Morrison configuration of the band while on the Europe 72 tour, Garcia wasn't very complimentary toward the band.

"I never liked The Doors," Garcia told Blair Jackson in the book Conversations with the Dead. "I found them terribly offensive…when we played with them. It was back when Jim Morrison was just a pure Mick Jagger copy. That was his whole shot, that he was a Mick Jagger imitation. Not vocally, but his moves, his whole physical appearance was totally stolen from right around Mick Jagger's 1965 tour of the states. He used to move around a lot, before he started to earn a reputation as a poet, which I thought was really undeserved. Rimbaud was great at eighteen, nineteen, and Verlaine – those guys were great. Fuckin' Jim Morrison was not great, I'm sorry." 

"I could never see what it was about The Doors," Garcia added. "They had a very brittle sound live, a three-piece band with no bass – the organ player (Ray Manzarek) used to do it. That and that kinda raga-rock guitar style was strange. It sounded very brittle and sharp-edged to me. Not something I enjoyed listening to. I kind of appreciated some of the stuff they did later, and I appreciated a certain amount of Morrison's sheer craziness, just because that's always a nice trait in rock ‘n roll." 

Jackson asked if Garcia had ever encountered Morrison offstage. "No, I never knew him, but Richard Loren, who works for us, was his agent and had to babysit him through his most drunken scenes and all the times he got busted and all that crap," he claimed.

"He's got lots of stories to tell about Morrison. I was never attracted to their music at all, so I couldn't find anything to like about them. When we played with them, I think I watched the first tune or two, then I went upstairs and fooled around with my guitar. There was nothing there that I wanted to know about." 

"He was so patently an imitation of Mick Jagger that it was offensive. To me, when The Doors played San Francisco they typified Los Angeles coming to San Francisco, which I equated with having the look right, but zero substance," Garcia concluded. "This is way before that hit song, ‘Light My Fire'. Probably at that time in their development, it was too early for anyone to make a decent judgement of them, but I've always looked for something else in music, and whatever it was, they didn't have it. They didn't have anything of blues, for example, in their sound or feel."

The above is taken from these two articles that are nearly identical but with different authors:

https://faroutmagazine.co.uk/grateful-dead-jerry-garcia-hate-the-doors/

https://ukdaily.news/why-did-grateful-dead-leader-jerry-garcia-hate-the-doors-370525.html