What are the best ways and methods to discuss with and guide a non-Sunni who is open to discussion, but attacks the Companions, in order to change their point of view?

Whoever attacks the Companions, or curses them, or diminishes their status, has no share in Islam. They should be advised with gentleness, kindness, and good admonition that this act is one of the greatest major sins and most heinous crimes, and that they must offer sincere repentance. If they repent, their companionship is permissible. But if they persist and the advice is not effective, then it is obligatory to abandon them; as Allah Almighty says: "And He has already revealed to you in the Book that when you hear the verses of Allah being denied and ridiculed, do not sit with them until they enter into another conversation. Indeed, in that case, you would be like them. Indeed, Allah will gather the hypocrites and disbelievers in Hell all together." The Companions are the best of Allah's creation after the Prophets, and Allah chose them to accompany His Prophet and was pleased with them. Therefore, whoever disparages them accuses the Messenger of negligence in his mission. The Quran and Sunnah have proven Allah's pleasure with them, and this pleasure negates the blameworthy characteristics that people of whims attribute to them. Every Muslim must believe that the Prophet, may Allah's prayers and peace be upon him, succeeded in raising a unique generation of Companions who conveyed the religion to those who came after them.