The thing I think David had to contend with was not whether it was good or bad, but the impetus with which it was conducted. His wife hated Ted before any of this. You can almost see the rage in her eyes about him when you watch documentaries on the subject. She led him in every way in getting Ted tossed away (and I think knowing this victory for her would come at the cost of her husband)-- David would have left it in his subconscious and Ted would have been found later (probably after more victims) in some other way.

David had to contend with the fact that you did the right thing because your hateful wife nudged you to do it, and that intent seemed to be more like 'how do we get rid of Ted' than 'lets save people'. AFAIK he is still married, so this is the key bit left out of these articles that David can't write our say out loud and you just have to read it between the lines.

I don't know that there were any good solutions for him. Probably the only way that wouldn't have felt like betrayal would have been for him to go up to Montana and deal with the problem himself, man to man, without the bit of giving him up to the FBI behind his back. Whether the prison time from that would have been worse than living with a lifetime of guilt, I have no idea, a difficult decision no doubt.

He made a decision. So did his brother as a consequence - non-contact. Continuing to barrage someone for years with letters someone does not want to receive (likely never read, either) in an attempt to assuage your own guilt is not loving behavior, and at worst is borderline abusive. The fact he felt he had a right to handle his brother's remains at the end, to the point he was berating the prison staff feels like it's indicative of the kind of thing I'm getting at. Ted was a person who had expressly desired to have nothing to do with his family, at some point you simply have to respect that whether you like it or not if you love them. This seems all about his own guilt and a lot less about his brother. I don't know if anyone here has ever been subjected to this by an estranged family member trying to make amends that will never be amended, but it really sucks to be on the other end of it, no matter what crime you may have committed.

Honestly I would feel guilty too. I would have made the same decision. However, I'd understand the consequences, and if I truly loved my brother as he says, I'd leave him alone, because that's what he wanted.