Is it permissible to skip Friday prayer and not pray behind an imam who does not recite Al-Fatiha well, makes many mistakes in reciting the Quran, and belongs to an association that permits innovations (bid'ah), defends the Rafidah, and slanders scholars?

You erred by alienating people, which led to your being prevented from leading prayers and delivering sermons. You should have been gentle and kind to them. As for now, you should advise them with gentleness and kindness, explaining the unsuitability of the current Imam for his imamate due to his clear grammatical error (laḥn jalī) in Al-Fatiḥah. If they respond, then praise be to Allah. Otherwise, look for another mosque for Friday prayer, or pray Ẓuhr if the Imam changes letters in Al-Fatiḥah in an error that invalidates the prayer. However, if his error is of a type that is excused, then pray Friday prayer with him, even if there are transgressions; for Friday prayer is performed behind every righteous and wicked person.