Yes and no.
Yes in the pessimistic view because human beings are selfish beings when it comes down to it and they can do many crude and cruel things to each other. Just by looking at history you can see that humans, over hundreds and hundreds of centuries have yet to realize that wars and fighting never solve anything. Yet wars, killing, death, and destruction still occur.
"There never was a good war or a bad peace."
- Benjamin Franklin (Letter to Josiah Quincy, September 11, 1783)
"On the whole human beings want to be good, but not too good and not quite
all the time."
- George Orwell
I agree with the second part of the quote but not really with the first in Orwells quote.

No in the optimistic view because not everything in the world is like that. There is plenty of good in the world and just because of bad experiences you can't make a blanket statement that all human beings suck. Granted at times it may seem like that at times. There is still good in the world and you can always start with yourself and though you will be fighting an uphill battle nothing is worse than losing hope and faith. No one said life would be easy.
"You must not lose faith in humanity. Humanity is an ocean; if a few drops of the ocean are dirty, the ocean does not become dirty."
- Mahatma Gandhi
"The ultimate measure of a man is not where he stands in moments of comfort and convenience, but where he stands at times of challenge and controversy."
- Martin Luther King Jr. (Strength to Love, 1963)

I know this is long and you don't you don't like reading long posts. Last and final quote. In life what is really important and what truly matters?
"Our lives begin to end the day we become silent about things that matter."
- Martin Luther King Jr.