Jesus had at least one Zealot as a disciple. Zealots were a group of people that had certain beliefs and wanted to have an outright war against the Romans to annihilate them. Also, nowhere in the gospel does Jesus say that all war is wrong and that you shouldn’t fight.
In Mark 11: 15 it says, “He entered the temple and began to turn out those who sold and those who bought in the temple, and he overturned the tables of the money changers and the seats of those who sold pigeons.” Even though there is no evidence of anybody being hurt, this is not the kind of thing a pacifist would have done. Most modern day pacifists would never think of knocking tables over and driving merchants out as true pacifism.
However there are also reasons for people to believe Jesus was a pacifist. For example, quoting from Matthew 5: 39, “Do not resist one who is evil. But if anyone strikes you on the right cheek, turn to him the other also.” This basically means that if anyone tries to fight you just let them and do not be tempted to fight back. A true pacifist would stand there and take whatever you did to them because they do not believe in fighting at all.
Also in Matthew he says “Blessed be the peacemakers; for they shall be called sons of God.” This definitely implies that even if Jesus was not a pacifist he wanted us to be. Jesus’ words to Peter when Jesus was arrested and he attacked on Jesus’ behalf were “All those who take the sword will die by the sword.” I think it’s pretty obvious what Jesus meant, that if you fight then you will be fought. He also reminded Peter that if God wished he had a legion of angels to defend him.
In Matthew 5: 43-48 Jesus speaks about the treatment of enemies. “You have heard that it was said ‘You shall love your neighbour and hate your enemy.’ But I say to you, Love your enemies and pray for those who persecute you.” This is Jesus saying that even though they are your enemies you should love them as if they were your neighbour, also even if people persecute you, you should pray for them like you would your friend.
One more reason that Jesus has been thought of as a pacifist was that when Jesus entered Jerusalem he was riding on a humble donkey. “Behold your king is coming to you, humble, and mounted on an ass, and on a colt, the foal of and ass.” Jesus was not riding in as a warrior king but as a king of peace.
Personally I think that Jesus was a pacifist but not a true pacifist. A true pacifist would not have been violent in any way when they turned out the merchants from the temple. However there is plenty of evidence that Jesus did not believe in fighting. “All those who take the sword will die by the sword.” This is the quote that makes me most think that Jesus did not like fighting. Even when he was arrested and condemned to death he did not want anyone getting hurt over him. The other thing that makes me think he was a pacifist is when he teaches people to “turn the other cheek” He does not want anyone retaliating to other people fighting.