Is it permissible to turn away from someone who backbites, even if it be one's parents, and at times not to focus on their speech, while still desiring to benefit from their speech that is not backbiting?

It is not permissible to listen to backbiting or to approve of it. One must rebuke those who backbite and avoid their gatherings if rebuking them is ineffective, unless those who backbite are one's parents. In that case, they should be advised gently and respectfully, and the conversation should be steered away from the forbidden. If they persist in backbiting, there is no harm in turning away from their words. There is also no harm in remaining present while disapproving in one's heart if departing would lead to harm.