Although I'm just a teen, I've been able to travel to many countries, and in my travels I once met an Israeli named Josh. I've since become really good friends with him, and a lot of my friends also Skype frequently with him. He's probably the nicest guy I've ever met. As far as guys go, he's a really clever and interesting one, but it seems that his brown eyes can pierce to the soul when the topic is serious. He's had a life so interesting I think they should make a movie out of it - all his travels and adventures. And over all that he's also a super good guy - I can myself see no flaw in this Jew.
Once in a while, I'll talk with my friends about Josh and they'll tell me things about him that I didn't know - say, that he's been to Russia. Sometimes we'll disagree - one of my friends said that Josh is a pretty funny guy (I think he can be funny at times too), while some of my other friends don't really see Josh as a witty guy. Another time we disagreed if Josh had sailed down a river in Lithuania or Latvia. But it's obvious they all know him - they think he's an all around incredible friend as well.
However, some of my friends completely contradict me and paint a nasty picture of Josh - they say he's an arrogant snob, he's a liar, he's cruel, he's a thief, etc. One guy even told me that he doubts this interesting guy really exists - he's probably just a made up illusion, or a seriously exagerrated. Some other friends don't slander him per se., but when they talk about my well-traveled friend, it's obvious they don't really know him and are just copying what I and other people have said about him.
In case you haven't figured out who I'm talking about, I'm talking about Jesus (Josh comes from the same root as Jesus). Sometimes Christians disagree about minor things about Him and His Father - if Jesus ever told jokes, if God predestines or lets man choose, or both, etc. Small differences in opinion are not the same as someone who raises a slanderous accusation against Him or says something about Jesus that just does not fit with His character - Him being a lunatic or a liar. Other people just don't know Him although they pretend they do, but it's easy to see through such superficialism.
The point I'm trying to make is that sure, Christians don't know everything there is to know about Jesus and all the things He is done - or even minor things about Him - so disagreements in minor things are to be expected. However, people who just don't know Him would say things about Him that just go against everything Jesus is. Saying He is not one with the Father is calling Him a liar or a lunatic, things which He most certainly is not. Christ is a person to be known, and among the people who know said Lord are disagreements found.