Defending against an attack is by definition, acknowledging and reacting to it.  Thats not the same as ignoring the attack.  In the example of the kids, defending would be explaining to them that they are being unkind, or putting your fingers in your ears.  Ignoring them is walking on by with no response.

It need not be children in the park, it could be a person in a car hooting their horn at you in traffic, you dont need to respond to that, just mark that person up as a nutter.  You could start honking back, give them some gestures, or even get out and start remonstrating with them, but none of those choices will have any significant effect on the heavy traffic, or that persons impatience, which are the root causes of their behaviour.  Should they be attacking you for situations beyond your control, no absolutely not, but there isnt a damn thing you can do about it.

Im just concerned with the statement of 'obligation', we are not obliged or duty bound to defend against attacks.  If we all start responding to all attacks, the world will go to shit pretty quickly.

Im not tearing down your post, honestly.  I just cant stand by and see people told they are obliged to attack others in response to violence, and that that is a morally acceptable solution.