Mathew 18:15

​The enemy you have attained off the witness of another.

When someone approaches you speaking bad about another, instead of responding,
"That situation is between the two of you, alone." 
[Mathew  18:15]

You come in (agreement) with them, just from what they told you. 

So, the conclusion of the matter is this, (Guard your heart) if someone is speaking against (anyone) and at the end, they do not suggest prayer, do (not) participate, no matter how juicy and interesting it may sound. 

Do not stay, go on your way, and the Lord will be pleased and reward you for your actions.

Proverbs 4:23, which says,
"Above (all) else, (guard) your heart, for (everything) you do (flows) from it".