Harrell is an extremely interesting and dedicated individual. His knowledge and experience make him a valuable instructor. However, I've come across enough about him/from him to know that his life experience doesn't resemble my life very closely. His lessons, sober as they are, need to be put through the filter of "how relevant is this to my situation?" I'd extend that to most advice.
One of his civilian involved shootings made the news years ago. He killed a man, and was initially jailed for it. Though he was later cleared of charges ––self defense or defending his wife, if I recall–– I certainly can understand where his vigilance comes from. It must have been a harrowing experience. Leaves one remembering that if you shoot someone, even if deemed justified, you will be dealing with it for a long time and your life will be seriously affected.
He comes off as a man with great integrity and strength. Down to refusing donations for his treatment and hospice. I hope there's a lot of community around him.