Often our Lord’s command “Judge not” is understood in terms of the saying ‘If you have nothing nice to say, don’t say anything at all’. And though it is true that scripture calls us to listen often and speak rarely (James 1:19), Jesus statement should not be understood to mean that Christians should never criticize or otherwise make judgments about spiritual matters. It is apparent that Jesus did not mean that we must never judge but not to judge in the manner which He went on to explain in detail (Matthew 7:5-7). This is confirmed when see that our Lord Himself, in another context, tells us that there are right principles with which we must judge: “Judge not according to appearance but judge with righteous judgement.” (John 7:24).
Furthermore the scriptures command us to “discern” (Hebrews 5:14), “test” (1 John 4:1), “reject” (1 Timothy 4:7), “examin[e]” (Acts 17:11), and “not believe” (Mark 13:21). Thus we are not required to be open to every teacher or word that we hear, nor to passively or silently accept their teaching, but to use our spiritual discernment as guided by the scriptures to embrace the truth and reject the lie.
“The simple believes every word, but the prudent considers well his steps.” Proverbs 14:15