Despicable behaviour

I don't understand it.

I don't understand why some people are so lacking in decency that they feel they have a right to make the whole world miserable.
I don't get why some people feel a need to drag others down to their level of misery; just because they lack the grace or gratefulness to find joy in life, they feel a constant need to bring the world around them to a screeching halt.

What is it about these people?
What makes you so special that you feel entitled/obligated to drag the people around down with you?
If you want to be miserable, go right ahead, but at least have the decency to keep it to yourself, instead of throwing your temper around and then expecting the world to treat you like a decent and respectable adult.
Such people are proverbial fools; they're the kind of people who curse at telemarketers, abuse cashiers, or make ludicrous demands of the people around them.
They are selfish, self-absorbed, self-centred, mean-spirited, contemptible and despicable little people, who walk around as if the world owes them something.
These are the people who yell at the people who serve them, who think that raising their voice and making demands is what will get them somewhere.
It might get them what they want in the short run, but the rest of the world will never ever respect or love such people.
These are the people who really believe that "the customer is always right." The truth is, "the customer always thinks they're right."
They walk around acting like the whole world is their enemy, and for their efforts, most of the world will gladly oblige them.

Truly, these are the types of people who can turn a party into a funeral just by their presence. They are moody, uncontrolled, unhinged, unreasonable.
Pity the people who must live or work with them.

And yet, they are so pitiful and pathetic because of their temperament will make them so lonely, so unloved, so misunderstood and avoided.

God help me love them.