Is Christian morality based on the imagined words of an imaginary entity?
Nope. It’s based on the same ethic of reciprocity that forms the true basis of all human morality. However, some Christians have buried it under so much nonesense regarding consensual sexual behaviors or “thought crimes” regarding “right” beliefs, that many feel free to ignore it altogether. It can be found, among many other places, in Matthew 7:12, where Jesus calls this Golden Rule of the ethic of reciprocity the summation of ALL the LAW and the writings of the prophets.
Morality is based on the very simple fact that altruism is beneficial to humanity as a whole. Some people however think they can get better personal benefits by taking from people weaker than themselves. It was decided by some well meaning people that it would be a good idea to sell the idea of morality to people in a different way. So God was made up to be an all powerful perfect source for rules which would prevent them from being oppressive. The makers of this idea were numerous and they could not help but include some of their personal opinions in to the mix when they were writing all this out. This is why we don’t have a book of generic rules like be nice to people we also have some crazy off the wall stuff like pretty much most of the book of Leviticus. This is the birth of Christian morality. Some of it is just imaginary and some of it is based on very secular common sense.