good is not certain.
Keep the techniques he know to handful number of vital people is better.
If the future changes too much he will lose his advantage being a time returner
but there are a few peope who were good and tried to hold up humanity in his last life, would'nt it be very important and helpful for them to survive? like that leader guy (lin i think?). as it stands i think it's very egotistical of him. it's not like other people are not evolving and it could give an edge to the people who care for humanit as a whole! right now it looks like he only care that his own group will survive.
It doesn't guarantee a 'good' guy turning bad. It's a survival world. Too much advantages being shared around, then he will end up to be just a mere pawn.
he could teach it to the good guys at least! why does he keep it just to himself!!!