If "A" tells us something negative about "B" let us not quickly believe "A" and form a negative opinion about "B".
It is sad how easily we form our opinion of people from what we hear from others before even trying to get to know that person and trying to find out what the truth really is.
What we hear may not always be correct because they just may be repeating what they heard or felt. If truly concerned to sort out issues it is better to get "A" n "B" face to face and sort out issues.
For our eyes and ears may deceive us.
Proverbs 25:7b & 8a "....what you've seen with your eyes do not bring hastily to court....."
Proverbs 25:9b " ...do not betray another man's confidence..."
1 Thessalonians 4:11 "...and to make it your ambition to lead a quiet life: You should mind your own business and work with your hands, just as we told you."