I have 4 step kids, 3 girls (well, one young lady, two girls) and a young man (who has cerebral palsy and cannot defend himself).
If anyone, regardless of age, mental state, or gender ever did anything to threaten the physical, mental, or emotional well-being of one of these persons, they could take me to jail and hold me for trial after cleaning up the greasy spot that offender once occupied. This can also be applied to any number of family members, my wife, friends, and my pets.
Legally, I'd be "wrong", and I know this very well. However, morally, I believe I would have every right to dish out this type of response to such a situation.
I understand the father in this situation has crossed a "legal line", and must face the consequences, but I totally support his reaction. The 71 year old dude, no matter why he did what he did, needed the wakeup call he just received, and should get an even more severe response from the legal system, but he probably won't.