Can it work that there are certain numbers of people in a community or around the world, who if they think good thoughts, they can overcome the destructive thoughts?
On one plane, yes. But on the physical plane, destructive energy is a very dense energy that overtakes most things in its path.
An angry person has a much greater chance of making other people around them angry than a happy person has of making people around them happy. Negative energy is highly contagious.
Why is that?
Because it is defense survival energy. Alert, alert, danger, danger. Hurry, hurry, scurry, scurry. All life responds to that for self-preservation. It is hard-wired, so it is much easier to infect because there are neural pathways that are already highly sensitized to that. Positive energy is more subtle.
So how do we build the neural pathways for a sense of peace and happiness?
The answer never changes. Meditation. Spending time in nature. Removing oneself from negative influences of modern culture. Reading positive material. Spending time with positive people.