He fought for socialism and he stayed a socialist - but he became a enemy of Stalinism.
The brotherhood and spirit of the socialist militia he was in, he praised as real and something he never experienced before or after.
My interpretation was that he was always anti-authority, but his experiences led him to believe that an authoritian figure will always try to grab power and it doesn't matter what `side` they say they are for, power is their aim.
True he liked the spirit of his socialist militia but by the end I think he felt its spirit had been crushed and abused by others.