Being Left inclined does not make a person evil; in many cases it is precisely because they would like a better world and want increased “good”. But what “good”/Good do they seek? What is the authority of the “good”? Can we really reason that Marx and Alinsky are better examples of “good” than Jesus Christ? Really?
The Good of the Will of God is often different than the “good” that is defined by most of the world.
There are soft-core Lefties who just want a decent world for everyone (good motive, bad means) and you have hard-core Lefties who actually understand what they believe and its consequences.
So what to look at when pondering “foundational Good”?
Current Rome?: No. Our political leaders? No.
My suggestion is that we return to classic reason. Aristotle being perhaps the most accessible religiously neutral figure that pursued Good.
From there we may rediscover the best of Christianity which under-gird the whole civilization. You may no more eradicate it from the West with a good outcome than you can remove the spine from a healthy person. How do you discover the best of Christianity as it is applied and lived in the world? Through the lives and writings of the Saints.