Re: causing no (serious) harm
The attacker may well have chosen to attack you but you have chosen to retaliate and chosen what form and how that retaliation will be carried out. Forcing someone to the ground and/or inflicting pain by choice (you could choose to simply evade or get hit) is inherently violent. By carrying out the technique in the knowlege of it's effects you are intentionally harming someone, even if you desire not to. This is violence. If you had no such intention you would not be performing the technique. You cannot choose not to halm someone and halm them at the same time.