I've often thought not to do a full breakdown of posts like these, and while you are correct that it often serves little purpose in persuading the individual being quoted, it does have value to the community at large.
I may not persuade him (though it would be great if it did and it has on occasion) but it might persuade someone else on the periphery. Another member, a lurker or a guest.
And of course, there is the community factor itself. For some, it's entertainment. For others, it stokes newer debate. So in that sense, I may not be doing a full breakdown for the sole benefit of whom I quoted but rather for the benefit everyone else.
Like they say, when you engage in debate you're not doing it for the sake of your opponent but for the audience.
My Console Library:
PS4, PS3, PS2, PS1, WiiU, Wii, GCN, N64 SNES, XBO, 360
3DS, DS, GBA, Vita, PSP, Android
Top 6 this generation:
Bloodborne, Sekiro: Shadows Die Twice, God of War, The Legend of Zelda: Breath of the Wild, Dark Souls III, Red Dead Redemption II, Rock Band 4