I am convinced Christianity stands or falls on the doctrine of total (pervasive) depravity. It's the cornerstone around which everything else is built.
To understand total depravity, study World War One (the Great War). I'm fascinated by the fact that there was no particular reason for the war's start (the world was in a global prosperity boom), the people fighting didn't have much animosity for each other (front-line troops respected the men in the other trenches more than their own leaders), and the war had no real end (both sides ran out of soldiers, but the Germans surrendered because America was bringing fresh troops over to Europe). In fact, while we make a distinction between World War "One" and "Two" it's really the same ongoing conflict resumed a generation later after the population of the warring countries recovered. Here we have millions killed and maimed for ... historians haven't decided. No one really knows why the war started or why people fought in it. Other than the fact that they were totally depraved and just enjoyed it. The world as a whole gave in to its carnal nature for four or five years.
World War One is a tiny slice of history, forgotten by most today, but it's a microcosm of the totality of history. I can't find one chapter in human history when total depravity is not on display. If a belief says something about the human condition, I do not know where else we could turn to see if the belief is valid other than the laboratory of human history.
Any consistent and rational view of the world must take the fact of total depravity into account. Or else the person who believes this view will not be able to understand the world. The world will be confusing and uncertain, and the person's beliefs will be unreliable. Thereis no way to argue against total depravity because the evidence is overwhelming.
Other than Calvinism, I have never found a philosophy or religious belief that doesn't say mankind is basically good. (If anyone ever finds one, let me know.) The only way that a belief can maintain that people are basically good in the face of the evidence of history is to say that something prevents this goodness from showing. But what? Every belief picks something different, and that alone is a red flag: Why can't they agree? Each belief tries to say that if what they pick is eliminated, mankind will be basically good once again (even though mankind has never been basically good at any point in history). People labor at eliminating from society whatever the current belief says is wrong, only to realize it's impossible, and move on to another belief which is equally impossible.
Christianity is different. Or, at least, Calvinism is different. Most of the "Christianity" I see today is not truly Christian. The current idea of Christianity seems to be that God takes something already outstanding, the awesome mankind he created, and just makes it a little better. Christianity is a process where God does himself a favor by taking a person and coaching and developing their greatness and making them live up to their potential, much the way a major-league ballclub invests in a minor league development program for their draft picks. This is false Christianity.
Calvinism says mankind is totally (pervasively) depraved, and is incapable of saving himself. If there's anything true in this world, it's that fact.