It is all a part of the evolution of astronomical science.
Originally "planet" as coined by the Greeks meant "Wanderer" and referred to any astronomical object that was not fixed in relation to the stars. Both the sun and the moon were considered to be planets once, along with the other 6 naked eye planets (though Uranus borders on the limit of visibility). It wasn't until Copernicus, Galileo and Kepler, that there was the first revolution in the meaning of "Planet" (although Aristotle did start it 2000 years before
). In fact it wasn't until the 1990's that the Church recanted their comdenation against Galileo for his heliocentric belief, that the planets orbited the sun and not the earth.
This current debate is just another step in that evolution.