The definition of a Christian is not actually defined well, except you believe and follow Jesus Christ.
I do get you on your statement that some of the most judgemental and condeming people tend to call themselves Christians.
I grew up being taught to follow the 10 commandments and this was being a Christian. I do follow them today. One of the commandments is to not judge. So one would assume if someone is judgemental towards others and condemn them for anything they do would make them not a "Christian"
I myself, would not judge anyone for any reason. I live my life in a very calm, caring sort of way.
By my definition, I am a realist, I follow the commandments, I would say I consider myself to be know as a Christian through my actions. I am not a self professed Christian. We are taught, it's not what we think of ourselves that make us who we are, it is the light we send out through our actions that make us who we are.
I have found, by following the commandments it makes my life easier. They are a great group of rules no matter what your faith might be.