When does judging others become a sin?

Today, many folks use their position in the body to pass judgement on their peers, and it seems to be in the name of only wanting to help a fellow brother or sister to sin and go to hell.

One of the problems I had with WOF folks was their good intentions. Intentions that were being led of their understanding of scripture, and obedience to the Holy Spirit to let another brother or sister know that their place in Christ, was lacking what they possessed, and they only approached that poor soul to help them avoid making mistakes that would or could keep them from living to the fullest potential of God in their life.

I became weary of such good will, as I was being told that my illness or disability was all of my own doing because it was evident I was not following or walking as close to God as they were or believed I should be.

So, when does our concern for another's status in Jesus become offensive and sinful? When does our concern for another's walk go too far? And how do we know when to back off, in order to "NOT BRUISE the fruit?"

BTW- my example of WOF believers being meddling or over aggressive, applies to well self professed, well studied Baptists too.