The problem is...

...you're still assuming guilt over innocence. Every argument you have is wonderful and I'd agree 100% if not for the fact that they all hinge on the assumption of guilt. We don't KNOW he was guilty and we can't pronounce him so without a trial by jury. Everyone just seems to be assuming that the father was correct and so he did the right thing. But, again, what if the father was WRONG? Human beings are, as Neil DeGrasse Tyson says, "poor data taking devices." We see things wrong, make mistakes, and get details that are right in front of our faces completely ass-backwards all the time. The father's word on this (even if he truly believes what he says to be true) is just not something we should be accepting as true and accurate by default. If the father was wrong, then he beat an innocent man to death because he didn't stop to find out what was actually happening. So the girl screamed? Maybe the guy also heard her scream and came to help. We don't know and we can't assume.

-BB