I see acts of kindness everyday. I've never lost faith in humanity.
Watching the "nightly blues" can make one ignore the fact that out of the (7 Billion plus) people who inhabit this earth only a small percentage of people are actually engaged in negative activities.
If one isn't careful they could end up ignoring the fact that nothing bad is happening on their street, in their neighborhood, or town.
Nevertheless perception is reality!
Whatever one chooses to focus their attention on the more of it they will see. A handful of bad news stories each night causes them to ignore everything else. Historically there have always been shocking things going on dating back to the start of mankind.
And yet many choose to ignore volunteers, emergency workers, and countless others who risk their lives or sacrifice for strangers daily.
Every hour of the day someone is donating blood, organs, money, clothes, or time to help fellow human beings (they don't know).
Watch any world disaster unfold and you'll see nations from all around the globe pitching in to provide food, medicine, water, and financial aid.
Twenty-six countries were involved in the massive international search for the Malaysia Airlines jetliner flight 370 in the Southern Indian Ocean.
The song "We Are the World" raised over $63 million for humanitarian aid in Africa and the US. And there have numerous other charity events and concerts to help farmers, poor & underprivileged, sick and elderly people.
Annually there are coat drives, food drives, building homes for habitat for humanity, Doctors Without Borders helping people in third world countries. The list goes on and on!
According to a report from Giving USA; Americans Gave ($335.17 Billion) to Charity in 2013. It approached the peak seen before the worst of the Great Recession.
As you stated people who lose faith in mankind do so in the "moment". Whenever we choose to (narrow) our scope of the world it's easy to feel hopeless. We see what we want to see.