Yeah I felt bad when Marty and FCB had the argument, it does make you feel the rift between them and the dilemma they're in. I dont think either are completely right or wrong either;
Marty wants what he feels is the 'Right' timeline but has had to toy with people and manipulate them in order to set things back in motion, he doesn't like doing it and most times particularly when speaking to Young Emmett he really hates doing it. But if he doesn't he dooms everyone he cares for to be brainwashed by the citizen plus program or because of the undoing of everything in 1955 Marty's parents are reduced to their coward/drunkard personalities and Biff is still roaming round being a dick to everyone. He's also abandoned his parents and Jennifer when going back to 1931 based on the trust of FCB that all would be undone once they went back.
FCB on the other hand also genuinely feels his existence should still count, after all hes lived 70+ years with someone he loved, despite the disaster it caused in the future he can hardly be blamed for wanting to hold on to it or change it for the better despite its flaws. From his perspective 'Martin' is just as bad as Edna, wanting to 'Override' his personality for his own gain. Also he cares more for the fate of Edna, which he now learnt from Marty lives an extremely lonely life, and doesn't see why someone should be doomed to misery if it can be helped. Not to mention his alternative self lived a similar, isolated life until Marty befriends him and timetravels and meets Clara.
Could go one but, yeah - great work storywise on this one Telltale, just get rid of that damn 'Temporal Duplicate' bug by the car of the futures tent

. I really cant wait for OUTATIME