I'm not in support of caging children, or murdering the parents.
Putting a child in a cage long enough to result in the child eating it's own skin in an attempt to survive is enough criminal negligence to require complete removal from society, imo. At this point the parents have clearly expressed their ability to initiate force against others and should have no expectation of gentle treatment at the hands of others.
I agree, I wouldn't handle them gently if they came anywhere near me or my family.
But I wouldn't go out of my way to have them whacked either.
And you wouldn't go out of your way if I went out of mine to whack them. That's the beauty of anarchy. On a more fundamental level, these people have given up on their right to live by forcefully putting the life of another in danger. As such, I have no responsibility to respect their life and a legitimate motive in opposing these people with force. You, on your end, have no motive to stop me from harming them in my attempt to save the child.