Because Jesus isn't the type of pacifist that you're misinterpreting him to be. Read Jesus' own words:
No peace, but division:
"Do not think that I came to bring peace on the earth; I did not come to bring peace, but a sword. For I came to set a man against his father, and a daughter against her mother, and a daughter-in-law against her mother-in-law; and a man’s enemies will be the members of his household." (Matthew 10:34-36)
"Do you suppose that I came to grant peace on earth? I tell you, no, but rather division; for from now on five members in one household will be divided, three against two, and two against three..." (Luke 12:51,52)
Concerning Christ's second coming:
I saw heaven standing open and there before me was a white horse, whose rider is called Faithful and True[Jesus]. With justice he judges and makes war. (Revelation 19:11)
Does that sound like a pacifist to you? Do you now see how you have completely misinterpreted who Jesus Christ is? Pick up your bible, blow the dust off of it, and read it.