First, if you believe people are born good, you will attribute evil to forces outside the individual.
Not true, if don't believe in a supernatural being who created the world then it is hard to attribute evil to an outside force.
Second, if you believe people are born good, you will not stress character development when you raise children.
Absolutely wrong, and it should be obvious that it is wrong. Not everyone, religious or not, makes it point to teach their children how to make the world a better place. But, stressing character development and overcoming the human condition is limited to people who think liek he does.
Third, if you believe that people are basically good, God and religion are morally unnecessary, even harmful.
He seems to unfamiliar with the diversity of opinion in the Christian church, let alone others outside the 3 major reveled religions.
Fourth, if you believe people are basically good, you, of course, believe that you are good -- and therefore those who disagree with you must be bad, not merely wrong.
Wrong. In my experience this kind of thinking is more prevalent in people who in absolutes, regardless of what their religious beliefs, or lack thereof, are.
Understanding that others can be good or bad, and that even good people commit evils acts is not limited to people who reject the notion that people are basically good. There are many varying viewpoints about how and why people commit evil acts and he is over vastly simplifying that discussion.