You don't necessarily have to be religious to practice the moral virtues. Four of the Seven Cardinal Virtues as defined over the centuries by the Catholic Church were Aristotelian cardinal virtues: prudence, temperance, justice, and fortitude. The pagans developed many other virtues as well, such as patience, honesty, and magnanimity.
Somehow I doubt, on the basis of his writings, whether Eric Alterman knows much about any of this. One might add to the list of virtues other concepts such as truth, which is little valued or practiced by liberal news reporters, as evidenced by their writings.
Morality and all of its associated concepts are based on the belief that some higher power is defining the correctness of human behavior.
Anyone who says I am immoral is no different than a preacher or rabbi telling me I am a sinner...
Plato's Euthyphro is a great illustration. Socrates advances the argument to Euthyphro that, piety to the gods, who all want conflicting devotions and/or actions from humans, is impossible.
Likewise, morals are such a construction of idols used by the Left as a rationale for them to demand compliance to their wishes in politics, which most often are a skewed mess of fallacies in logic.
Morals are a deceptive replacement for the avoidance of sin.
If a person believes in a God, it is the conviction of the Holy Ghost by which they are guided and not by the idolatrous vanities of morals constructed by others.
Which is really all there is to strive to obtain...the rest will take care of itself.
FMCDH(BITS)