> No matter the bad blood that can be present in a family, I just can't imagine how one can treat one's own parents this way.

Respectfully, you don’t know shit about the families of other people.

It is possible for a person to have subjected their children to life-altering trauma, and many years later be playing the sweet and lonely old person. There’s enough manipulative guilt already without strangers on the internet adding to it, or minimising the emotional wounds of abuse as “bad blood”.