John Lennon only spoke against revolution in that particular version of the song (Revolution) because he feared the revolutionaries wouldn't stand a chance against the police and military. He actually WAS for communist revolution.
Title: Revolution
Artist: John Lennon
"You say you'll change the constitution
Well you know
We all want to change your head
You tell me it's the institution
Well you know
You better free your mind instead
But if you go carrying pictures of Chairman Mao
You ain't going to make it with anyone anyhow
Don't you know know it's gonna be alright
Alright Alright"
http://johnlennon.lyrics.info/revolution.html
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The Lost John Lennon Interview
"Power to the People"
TA (interviewer): In a way you were even thinking about politics when you seemed to be knocking revolution?
JL (Lennon): Ah, sure, 'Revolution' . There were two versions of that song but the underground left only picked up on the one that said 'count me out'. The original version which ends up on the LP said 'count me in' too; I put in both because I wasn't sure. There was a third version that was just abstract, musique concrete, kind of loops and that, people screaming. I thought I was painting in sound a picture of revolution--but I made a mistake, you know. The mistake was that it was anti-revolution.
On the version released as a single I said 'when you talk about destruction you can count me out'. I didn't want to get killed. I didn't really know that much about the Maoists, but I just knew that they seemed to be so few and yet they painted themselves green and stood in front of the police waiting to get picked off. I just thought it was unsubtle, you know. I thought the original Communist revolutionaries coordinated themselves a bit better and didn't go around shouting about it. That was how I felt--I was really asking a question. As someone from the working class I was always interested in Russia and China and everything that related to the working class, even though I was playing the capitalist game.