Obama's farewell speech -- does he believe what he says?

I watched Obama's farewell speech and had a new revelation. While in certain occasions he did take more credit than he deserves, or exaggerate what he has accomplished, I do believe he spoke from the bottom of his heart and he truly believes that human beings will ultimately choose "good".

Do you liberals believe that men are more capable of good, than self-centered acts (doesn't necessarily have to be evil), that ultimately, benevolence and altruism will win? At least Obama's reasoning for welcoming people from all nations and cultures seemed to be based on the belief that, regardless what you had in mind before you came to America, you will see the greatness in this nation and will ultimately choose to cherish it and do what's right and for the betterment of this nation.

I don't know, but seems like history doesn't provide enough evidence that this is the case. American troops committed rape, torture and mass murder of civilians in the Vietnam war, according to veteran's accounts. Look here:

http://www.alternet.org/vietnam-war-was-worse-you-could-ever-imagine

Same thing in Iraq. In fact, I personally spoke to an Iraqi vet who told me he saw his superior torturing and killing 2 civilians "just for fun" -- why would he lie if it were untrue? Anther account when I was in Okinawa, Japan, where the local tour agent told me raping of local women by American troops stationed there is "very common". All that, in the end, is evidence that in the absence of punishment and retribution, humans would almost always choose to satisfy their true desires.

Men certainly could to act selflessly, perhaps those like Mother Teresa or the Dalai Lama, but men could also elect Hitler, support Mao Ze Dong's cultural revolution, or killing millions in the Killing Field in Cambodia. Everything happened in history is very much like what Thomas Hobbes believed, that is "Take away our law and social convention, and we will fall into the state of nature. Even in our state of civilization, we carry with us reminders of the consequences of natural liberty."

Arguments for more rules and regulations also proves my point, that in the absence of those regulations, men again, will do what benefits themselves and not act benevolently -- you have to incentivize someone to act in a certain way.

So what evidence is there to say that ALL immigrants will come and embrace America's philosophy and act unselfishly?
What incentive does the "poor" have to work hard instead of just taking welfare money indefinitely, or just stick with his / her current job because it pays as much as a job that requires another degree?
And how would that all work together with free education (when there isn't an incentive to get one)?