Is this about the thread where you wrote about your nephew who is also some sort of your best friend and with whom you tend to have heated arguments about various topics where somehow your argument for him never makes sense?
If so, and others ENFPs are welcomed to correct me, I can give you my perspective of argument with them, since my best friend is an ENFP. If disagreements you two have are about topics of for example evolution (something that's not of some big importance to neither of you two) then bear in mind that he probably randomly chose side, especially if that conversation started like this: he asks you "what do you think about evolution, do you think it's probable or not?", then you say "yea, I do believe in evolution" and then you see him taking air and preparing for a heated conversation with you where he will be willing to say almost anything even if he doesn't believe in things he's saying just for the sake of argument.
Over time I got to realize that for them that way of arguing about things is fun, and they actually don't care if they are right (with some exceptions when the topic is something very personal to them), they just want to discuss things with someone whose intellect they actually value and with whom they have impression that they are learning and expanding their own mind while attempting to help you do the same with yours. I do value their ways, but for me sometimes that way is not optional, or if my ENFP friend goes to far in that discussion with her arguments I just find a way to end it so nobody gets hurt. So if this is your situation with your nephew, I'd say to take his attempts to argue over things with you as a compliment.