Ahhh, but mankind and civilization are an ill defined construct of humanity that is by no means uniformly defined.
Even as written, with good intentions and meaning, so too was the arguments of a notorious leader turned dictator that plunged the world into World War II; with the same very arguments of destroying those who were deemed to be destroying the world for others. Ironically, even that definition of who was destroying the world, was so fluid that from beginning to end of world conflict, it no longer resembled the original movement that gave it momentum. The bandwagon effect of human discourse is a dangerous thing.
But with the simplistic logic bounded as a notion of goodwill and world peace then perhaps the time travel would be possible without Biff corrupting the original notion. Hmmm, that damned vicious cycle of human power and greed is back in play again. 🤷♂️ 🤦♂️