For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Tim Maas
Previously discussed at https://ebible.com/questions/19574-why-did-david-kill-two-thirds-of-the-moabites
Danny Hickman
David had sin in his life; he was an ordinary man. But the Scriptures don't depict him as a brutal man. That needs to be stated unequivocally and it needs to be understood as a staple truth. The Bible ain't trying to say that David was brutal anywhere in any narrative.
The Bible tells us a lot about David. He got angry with a fool named Nabal, and intended to kill him and his whole clan. Nabal had disrespected him and David's pride welled up in himself and he set out to destroy all that Nabal owned (I Samuel 25). He might have gone through with exacting prideful revenge against the man, but Nabal's wife Abigail interceded. When she got to David, she told him (paraphrasing):
'You don't wanna do this. My husband Nabal is a fool; he ain't worth what you're getting ready to do to your reputation.' But she was humble about her part in stopping David. She said, "The Lord has held you back from coming to bloodshed and avenging yourself with your own hand" (1 Samuel 25:26). David was impressed! He relented!
David's 'Sin Depiction' in Scripture is for adultery and conspiracy murder. He got Bathsheba, the wife of one of his military leaders (Uriah) pregnant, and tried to hide his sin by having Uriah killed in battle. He conspired with his top field soldier Joab and had it done (2 Samuel 11).
Of this awful deed, David was guilty. It portrays the sin in David's heart. He had a boatload of pride. He was willing to kill to keep up appearances.
But.. when convicted, he repented.
Danny Hickman
Pride... if you wanna bring a convicting charge against David, make the charge to be Pride.
You don't believe my assessment? Listen closely to David's oldest brother Eliab when David showed up at the Valley of Elah during the impending battle between Israel and the Philistines. David asked what would be done for the man who was willing to fight against the Philistine giant, Goliath. Here's Eliab's accusation to David:
"Why did you come down here, and with whom did you leave those few sheep in the wilderness? I know your pride and the insolence of your heart..." (1 Samuel 17:28).
Eliab was spot on!! David was a very prideful man. But he was never even accused of being brutal. That's because he wasn't that kind of man.