Often people use claims of hearing from God to add authority to what they have to say; so if we reject their message the inference is we are rejecting God. It is the kind of tactic used by so many false teachers and false prophets.
At one time I was quite casual in my use of terms like “the Lord showed me” and “the Lord taught me” and “the Lord revealed to me”, but I later realized that the Lord had done no such thing because some of those “revelations” were totally contrary to scripture (but my knowledge of scripture at that time was limited to proof texts drummed into me by the teachers I regularly listen to – and those texts mostly did not mean what they were being used to support).
I thought I was hearing God’s voice but it was man’s – because that is all I ever listened to.
These days I am more confident of what IS God’s voice but I am less likely to say “God told me…” or “God showed me…” I just try to speak (or write) His truth, but if I do get it wrong, I’m not crediting God with my mistakes and I pray that He will make me aware of them.
Scripture makes it clear how many people would be unwilling to accept truth even when it is made most clear. Examples that come straight to mind are:
1) The statement “If they do not hear Moses and the prophets, neither will they be persuaded though one rise from the dead”
2) The fact that Jesus’ physical presence and personally witnessing His teaching and miracles was not enough to convince so many of who Jesus is.
3) When confronted by God’s wrath, living men (who recognize the truth of what they are experiencing) are more willing to have mountains fall on them than to admit their error and turn to Him in repentance.
So many people resist truths that affect THEM personally requiring action from THEM. They are more likely to shout AMENs to words that require change from others. Blanket condemnation of the “lukewarm-church” is popular among those who want to portray themselves as being red hot for God, and everyone else much cooler. But words about being blind wretched and naked are not so popular when the finger is being pointed, more personally, in our own direction.