Interestingly, this means that in the case of strict monotheism as in Islam or Judaism it's all but nonsensical to talk of God as being "good"; given a God consisting of 'three persons' as in trinitarian Christianity it makes a little more sense, but it would still be an extremely limited kind of morality or goodness from the interplay of three more or less identical, omnipotent beings. A liberally-minded believer might speculate that perhaps that's why the 'morals' of the Tanakh are so barbarous, the early efforts of a deity struggling to come to grips with morality in unfamiliar social dynamics, but learning more as the millennia pass and coming back to offer some slightly better tips in the New Testament. Maybe in another few thousand years it will actually be accurate to say that God is good!
If you see morality in the way I described, it would make no difference to our sense of morality whether God exists or even if he is necessarily good or bad. Who cares? We would want to do the right thing regardless of the answer to any of those questions. The existence or non-existence of God would then be some question of idle curiosity, of no more relevance to every-day questions and dilemmas of ethics and morality as the existence or non-existence of parallel universes or something.
This reliance of external authority for moral decision-making is a little like a little kid who thinks that the only way they will know what the right thing to do is is what mommy says about it. They cannot imagine being able to have the maturity, knowledge, and judgment to decide for themselves. That's fine for a 5- year-old. But by the time your kid is in their late teens, you would think most parents would be proud that their kid has the maturity and judgment to make difficult decisions and judgments on complex matters without constantly asking them.
Moral issues can be decided on their own merits. You do not need external authority- whether parents, priests, or otherworldly deities' opinions. I don't think religious people have that level of maturity or confidence in their own knowledge or judgment. Having met and talked with them, maybe that's not such a bad thing after all.
The only problem then is that they are like blind people who always have to be led around by someone else- a priest or something. That's usually too much power for a wily priest or politicians not to exploit and manipulate for their own purposes- and history seems to provide ample evidence.
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"History, I believe, furnishes no example of a priest-ridden people maintaining a free civil government. This marks the lowest grade of ignorance of which their civil as well as religious leaders will always avail themselves for their own purposes."
-Thomas Jefferson to Alexander von Humboldt, Dec. 6, 1813.
"During almost fifteen centuries has the legal establishment of Christianity been on trial. What have been its fruits? More or less in all places, pride and indolence in the Clergy, ignorance and servility in the laity, in both, superstition, bigotry and persecution...In some instances they have been seen to erect a spiritual tyranny on the ruins of the Civil authority; in many instances they have been seen upholding the thrones of political tyranny: in no instance have they been seen the guardians of the liberties of the people. Rulers who wished to subvert the public liberty, may have found an established Clergy convenient auxiliaries. A just Government instituted to secure & perpetuate it needs them not.”
-James Madison
"The experience of the United States is a happy disproof of the error so long rooted in the unenlightened minds of well-meaning Christians, as well as in the corrupt hearts of persecuting usurpers, that without a legal incorporation of religious and civil polity, neither could be supported. A mutual independence is found most friendly to practical Religion, to social harmony, and to political prosperity."
-James Madison
"Mingling religion with politics may be disavowed and reprobated by every inhabitant of America...All national institutions of churches, whether Jewish, Christian, or Turkish (Muslim), appear to me no other than human inventions set up to terrify and enslave mankind, and monopolize power and profit."
-Thomas Payne