Discernment is not judgement.
IMHO:
If I can read the Scriptures, and they say, for example, that adultery is a sin, then I know, from God’s Word, that adultery is a sin. That is discernment.
If I know that adultery is a sin, and I get angry/reject/hate someone who willfully and repeatedly practices adultery, that is judgement.
So, I can tell the adulterer that he/she is sinning, but I don’t reject/hate/etc. because judgement does not belong to me.
That’s the way I think about it, and it’s harder to put into practice than it is to write about it.
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See http://biblehub.com/greek/1252.htm
Strong's Concordance
diakrinó: to distinguish, to judge
Short Definition: I distinguish, discern
Titus 3:10 A man that is an heretick after the first and second admonition reject;
2 John 1:10 If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed:
Romans 16:17 Now I beseech you, brethren, mark them which cause divisions and offences contrary to the doctrine which ye have learned; and avoid them.