Many base their belief that they should not judge anyone on the verse from Mathew 7:1,
This is repeated in Luke 6:37,"Judge not, that ye be not judged."
"Judge not, and ye shall not be judged..."
In John 12:47, when speaking to the crowds, Jesus said,
He did go on in the next verse to say there was one who would judge those who rejected His message, the word."And if any man hear my words, and believe not, I judge him not: for I came not to judge the world, but to save the world."
Peter tells us in Acts 10:42 that Jesus is
the Judge of the quick and the dead.
Paul warns us about criticizm of Christian's who are weak in the faith in Romans 14:3 when he says,
Additional comments are made about judging fellow Christians in verse 10 and 13."Let not him that eateth despise him that eateth not; and let not him which eateth not judge him that eateth: for God hath received him."
However, in 1 Corinthians 5, Paul seems to go against this tide and clearly teaches that the church is not to tolerate those who call themselves Christian but are knowingly committing sins.
Based on these, it would seem that we are:
(1) Not to judge non-Christians but we are to tell them the Good News, God will convict them of their sins and motivate any necessary change;
(2) Not nit-pick those Christians who are weak in the faith (and we don't necessarily know who those are); but,
(3) Not allow open sinfulness within our assemblies.
Some would say that to whatever extent you judge, to that extent you will be judged.
What say you?

