i was talking with a good friend and came upon the idea of why its easier to unite people against an enemy than it is to unite people for a common good.

1) its easy to demonize someone.
we all learn this in the first grade. we make fun of others to hide our own weaknesses.
it also makes us feel better about ourselves, because it makes us feel other people are beneath us.
it makes us feel that we are not the ones lacking in whatever.

2) its easy for people to agree that someone is an enemy.
its much easier to focus on the differences between 2 people than it is to focus on the things in common.
usually because its those differences that we all find key to our personality. its those differences that make us unique and so we value those traits very highly.
the traits we all have in common are valued less because everyone has them. true, it is essential to daily life that 99.9% of us have working eyes -but that quickly becomes taken for granted and we focus on the traits that make us different from other people. its those differences that we use to identify ourselves as individuals.

3) its easy to use fear as a motivational tool.
i believe there are social psychology studies demonstrating that fear, when paired with a path to avoid that which is feared, is the most effective means in motivating people to quit smoking (for example).
if you present something that makes people anxious and fearful, you stimulate a fight or flight response, which is genetically inherent motivation -motivation to escape or defend from danger.
you then harness that motivation by showing a direct path to escape the danger. make it an easy decision for the person experiencing fear to make, because their decision making ability is impaired by the emotional response.
it is easy to manipulate people using fear.

4) its easy to earn someone's trust by commiserating a common enemy.
first, because of reason 1. it makes people feel better to look down on other people.
second, because of reason 2. it gives 2 people something in common. they both hate X.
third, because of reason 3. the manipulator has saved the person from danger.
forth, because of reason 4. if the manipulator can pretend to be affected by the fear, the pair can then commiserate their feelings of fear and
fifth, bond over working together to escape/defeat an enemy.

5) its difficult to unite on what we have in common.
maybe because we are all inherently "enemies" in some sense, with our differing points of view.
we can all agree that murder is wrong, and can thus unite in demonizing murderers. but that leads to more challenging questions:
what do we do with murderers? kill them? imprison them? reform them? hospitalize them?
what defines murderers? 1st degree? manslaughter? self defense? war? testers on animals?

so once the issue we fear has been conquered, we then have to decide how to proceed -and that can be very divisive, considering how many opinions there can be on the subject.