I do not think everyone claiming Jesus is just one big happy family. I think knowing Jesus, the real Jesus, involves knowing the truth about Him. I think there are many people claiming Christ and following something that looks vaguely like Christ but they are off. I it is important that people are following the real Christ and this may be what moves people to say things that seem judgmental to the people who hear them. When in fact their intentions are good. We wouldn't want someone we love continuing in heretical thinking. Isn't this why you share your beliefs with others? The early church was very careful to maintain Orthodox beliefs and worked hard to remove incorrect thinking. Unfortunately over the years we have seen devision upon devisions and that is how we have gotten to where we are today with a million different people claiming to worship someone with what appears to be many different faces. But truth is there is only One True God and not every one can be right about who He is. If 10 different people have 10 different Jesus', assuming that one of them actually knows the real Jesus, nine of them must be following someone besides Jesus. It is a dangerous thing.
However, I do not think that gives anyone the right to insult or belittle. That's just rude. I admire people who can address heresies with tact and in a helpful and non-judgmental way. It hurts to be told "you are wrong and don't really know Jesus, the real Jesus." Someone called me on my beliefs and it stung. I responded with anger and judgment towards her and what I perceived as an uppity attitude. (There were several of us and we all just really did not have ears to hear. We came from many protestant traditions: mainline, non-denominational, messianic. None of us were happy to hear what she had to say. She wasn't against any of us specifically. She was for truth.) She took a lashing for being so bold. It was really hard for her but her love for us and for truth, was bigger than her desire to be liked or accepted. Today, am so thankful for her love and that she was willing, because I was wrong. I was walking in heresy and did not care. I liked my beliefs. They were comfortable and relevant to me. Because of her wisdom and willingness to take me on (and many others) there has been a revival and many more people now know more of Christ and the truth than we did before. She completely changed my life, my thinking, my whole world view. Like I said, it was hard to be told I was wrong (and she got very specific), painful to the very core of me, but I was glad she was willing. Once the scales fell away and light was revealed I could see it all so clearly. May we all be willing to speak up so that our brothers and sisters will not be led astray by an incorrect Christ. may we all do it with Love and tact, though so as not to inflict wounds but rather to heal divisions and heresies.
I highly recommend the book Jesus of Suburbia by Mike Erre. He has a lot of good things to say about the importance of how we define Jesus. If we acknowledge that not everyone can be right, then it becomes important decide which is the real Jesus, which is heresy and which is a shadow of the truth. and once we establish that we can move towards looking for the truth and breaking with those untruths that hold us back but also that we love and feel so comfortable with.