Is the listener of backbiting sinful if he listens to a shaykh backbiting another da'i?

Backbiting is permissible for the purpose of warning against an immoral person (fasiq) or an innovator (mubtadi'), and there is no sin upon one who hears advice from someone warning against an immoral person or an innovator. However, slandering scholars and callers to Islam without justification is one of the greatest pitfalls through which Satan entices his allies. Therefore, one should be cautious of those who disparage people of knowledge with things that are not considered disparaging, or who attack them due to a difference of opinion. Knowledge should be taken from those known for following the Sunnah (definition) and supporting it.