It's either perfectly consistent if you go minute by minute, or consistency goes out the window without any murder.

1978: Some matter and energy materializes. It appears to be a human being. Where did it come from? It's impossible to tell; it has no past as far as we're concerned.

1978: Oh my god, the mystery human has just killed another human. They look kind of alike, I guess.

1978: The mystery human is now in prison; its lack of citizenship or identity ("yeah, born in 1952 my ass, you're clearly at least 50 years old") does not prevent its incarceration.

2017: Nothing of note happens. Mystery human would be eligible for parole, if he hadn't died behind bars in 1996.

I think the last part is key: comprehensible to humans. I see the paradox but it’s a logical one not necessarily a physical one. I’m not even sure what time travel really means. Do you look at a river and think to capture it exactly as it was an hour ago? Would it really be the old river then? If you did capture it and add a few extra drops then set it in motion would there really be a problem? I’d posit that the past does not exist except as a mental construct to begin with. A “present moment” doesn’t even exist, how could you have a past moment to return to?

You have it backward.

The only reason you managed to live into 2017 is because all the assassinations on your grandparents failed.

The only thing that will happen if you try to go into 1978 is that you will discover why you failed.

In 1978 the other you would be 1 year into their light-speed trip away from Earth. How can you kill them?