What is the ruling on insulting the Companions in Islamic law, and what is the evidence for it?

It is obligatory to love the Companions of the Messenger of Allah, peace and blessings be upon him, to honor them, to be pleased with them, and to accord them the status befitting them. For, loving them is a matter of religion, faith, and righteousness, while hating them is disbelief, hypocrisy, and tyranny. Scholars have differed concerning one who insults the Companions, and whether he thereby commits an act of disbelief, as insults vary in severity. Whoever considers permissible the cursing of the Companions, or curses all of them, or the majority of them, or curses any one of them specifically for his companionship, has disbelieved. And whoever slanders Aishah concerning that from which Allah has exonerated her, has disbelieved, due to the consensus of Muslims on this matter. An insult may be less than disbelief, in which case its perpetrator is considered a fasiq (transgressor).