Doc being scared of future info makes no sense
Even if your intentions are good, it can backfire drastically!
Sure, Doc, whatever you say. However..
..don't you ALREADY know quite a lot? Why is it OK to know about the time machine, about who the president is in 1985, about Flux Capacitor in action, tinker and modify a car that hasn't been invented yet, let alone modify a time machine invention that won't be reality until three decades later, watch video tapes that LITERALLY SHOW THE FUTURE, listen to your own speeches from the future, and so on and so on, but not a little bit more info that would save your life?
It makes no sense that Doc is COMPLETELY OK with all the knowledge he's handed about the future, he knows SO FRIGGIN' MUCH, but not want to accept a tiny tidbit that would save his life!
Why is it OK to know all this and to watch the video tape over and over, and to see the 'run for it, Marty!'-bit and hang your head dejectedly, but not let Marty realize you watched that part many times, and that you are trying to figure out ANYWAY what happens (otherwise, why watch that part of the tape and why try to hide it from Marty that you did?)?
None of this makes ANY sense. Let's say the info Marty has offered plus what he wants Doc to know is 100 units of information for simplicity.
Doc already knows about 85 units of information, but somehow SUDDENLY is completely against knowing the last 15 units. WHY would this make any sense? What is 'too much' about your own destiny?
Wouldn't it be only BENEFICIAL to know about your own future, because then you have MORE POWER to alter and change it to your liking, instead of having to go through it blind?
Furthermore, 'just as you have endangered yours' makes no sense, because Marty didn't endanger his own existence because of his knowledge of his own future/destiny (whatever), but because he ALTERED THE PAST BY HIS ACTION(S)!
So Doc is completely full of BS here, and none of it makes any sense whatsoever.