It really is an interesting question to ask people. Everyone seems to have very different and personal answers.
I agree. Many people seem to think we are on an inevitable march forward of improvement. To be fair, generally things seem to improve historically speaking. But that improvement is fair from inevitable. Backslide is always possible.
I don't think we are necessarily prone to "evil." As a social species, there seems to be some predisposition to working together and altruism for the good of the group.
I generally agree - we are social beings and prefer "community" to isolation. However, we have always recognized that to live peaceably in community requires all adhere to certain rules, restrictions on behavior - which I think speaks to our fundamental weakness as humans. I might cite children and what it takes to raise a responsible child to live in society responsibly - a fair amount of discipline and training is involved.
I do think that we are very capable of "evil" and that what people consider "evil people" is actually somewhat common. For example, Hitler didn't act alone. Look how many people fully willingly played a part in his regime, or Mussolini's, or Stalin's.
Perhaps this is just semantics. "Prone," "capable..." The possibility for "bad" behavior not only exists, but we've all - repeat, ALL exhibited it at some point(s) in our lives - be it lies, deceit, theft, anger, selfishness, hedonism, gluttony, indulgence, etc. etc. etc.
The bottom line is that if humans are to coexist, we need a certain social "structure" so we can coexist peacefully - and that because it's (and I'll merely appeal to millenia of history here) inevitable that without it, we'll find ourselves at each other's throats - Gene Roddenberry or no.
Everyone likes to think that back in the day, they would have been an abolitionist, or a feminist, or opposed Hitler. The fact is, most Americans originally supported Hitler. We were actually pretty anti-semetic back then.
Touche. Or Christians today were they in Pilate's courtyard 2000 years ago as he brought forth Jesus and asked what he should do with Him. How many would have screamed with the crowd, "Crucify Him!"
I've read several books about Germans and Hitler - some fascinating psychology there. A nation which has literally been the battleground for invading armies for centuries as they've had to pass through Germany to get north or south, east or west. The Germans had, over the centuries, learned how to live as a conquered people over and over again. I'm working now on another book called "Ordinary Men - Reserve Police Battalion 101" - how a group of ordinary people turned out to be vicious killers in Poland. Scary what we're genuinely capable of.