Of course there is no right or left "up there"; the references we see in the Bible1 about the righteous sitting at God's right hand just reflect the way people thought when the Bible was written.
Then, as today, the right hand is considered to be 'special' in some way.
Even for left-handed people, the right hand is used for 'righteous' duties, such as greeting another with a handshake, saluting, raising the hand to take an oath, or making the Sign of the Cross. Etymologically, left is related to twisted, crooked and sinister, whilst the words right (-hand) and right (correct) have the same Old-European roots.
The majority of people (around 90%) are right-handed; a trait called lateralisation, which is found in animals, birds, fish and even the antenna of insects, as well as humans. The right hand tends to be used more, is consequently stronger and by extension, righteous.
On the other hand, left has a negative image: weak, something that is left behind, left alone, leftover. And this is found the world over. Some cultures believe it is impure to use the right hand when using the toilet. In Japanese, hidarimaki means somebody's ideas are a bit twisted, spiraling from right to left.
For a couple of thousand years, Christian theology has said that we have all inherited the original sin of Adam. Yet it was only in the 19th century that scientists discovered that we are made of only left-handed amino acids. Coincidence? (Probably.)
In 1789, following the Scriptures, nobility sat themselves on the right-hand side of the president in the French National Assembly, leaving the left-hand side for the commoners. From this, we have the 'right wing' and 'left wing' in political speech.
The majority of right-handed people are cruelly oblivious to the plight of those who are left to suffer the handism in equipment design, from chain saws to guitars, vending machines to wrist watches, and can-openers to camcorders. Even the flush handle on the W.C. favours the righteous. But as W.C. Fields said:
"If the left side of your brain controls the right side of your body, and the right side of your brain controls the left side of your body, then left-handed people must be the only ones in their right minds."
William Claude Dukenfield (1880-1946)