Reading the OP link it doesn't sound that sensational, just tragic.
I think we can reasonably tell the difference between hitting someone to get them off your daughter, or beating them well past the point of getting the third person out of harms way. If he knocked him a few good times at it was enough to kill him, that's a tragedy. If the father just sat on the guy pummeling him into an unrecognizeable pulp, he's off into questionable legal territory.
The daughter is best served by parents that keep an eye on her when in secluded situations with other men, and being trained as best as practical to avoid/handle such situations (of which I can't tell in this article). Being prepared to shove a bat up someones ass is far less effective at keeping your children safe. Don't make it out to be so noble to kill people, when the entire goal was to keep his daughter safe. Remember that attitude when your daughter was drunk and stumbled on to some gun-hill-billy's porch at night and gets shot out of "self defense". Priorites people.