Is it permissible to pray behind someone who does not show respect, enjoin good, or forbid evil?

The statement "does not respect the young" by the questioner is very general and does not specify the actions of the Imam, nor whether they constitute فسق (transgression/immorality). As for abandoning enjoining good and forbidding evil, it is relative and varies according to people's capabilities. It is a communal obligation (fard kifaya), not an individual one (fard ayn). We have previously discussed praying behind an immoral person (fasiq), an innovator (mubtadi'), or someone disliked by the worshipper in previous fatwas.