Christians are judgmental by definition. According to the basics of the Christian faith those who don't believe in Christ will go to Hell in the afterlife, those who accepted Christ will go to Heaven. Since there is absolutely no evidence of either place in the actual Universe this is based on pure belief and one particular collection of disparate stories written over the course of several thousand years.
Their belief makes them divide people into two categories: Christians and non-Christians, good people and bad people, people of the right faith and people of the wrong faith (or lack of any faith altogether). Some of the denominations place high value in converting (as they say "saving") other people. This is exactly what judgment is: you think other person is wasting his/her life if they don't follow Christ. They judge the value of another person and act on their judgment.
Therefore, by the very essence of the Christian faith Christians judge other people. They might say they are trying to help lost souls, save their souls, help them discover the truth, etc. etc. but at the core of all this is a judgment call: that person is not worth the Heaven, that person will infinitely suffer for eternity just because he/she doesn't believe in their deity.
Curiously enough if you listen to almost any Christian sermon you would hear pastors judge other Christians more than non-Christians saying phrases such as "Some Christians don't understand...", "Many Christians think...", "I've met some Christians..." etc.
So, yes, Christians are judgmental by the very definition of their faith and they judge both Christians and non-Christians. They are equal opportunity judges of other people.