This is why we feel discipline is so important in our role as parents, amongst all the other important stuff.
We're not here to be our kids' best friends, or be liked by them every minute of every day. We're here to teach them the difference between right and wrong and help guide them to make good decisions.
To teach them to be able to stand on their own two feet so they become well rounded adults who don't expect everything to be handed to them on a silver platter (there's a difference between supporting your kids through life and letting them use you as a crutch forever).
To teach them to respect others, their property and their feelings. We don't want to raise bullies, we want our kids to be caring, loving and kind.
But also, to teach them be able to stand up for themselves when needed. Whether that be verbally or physically, if another kid is harassing ours and ours fight back, we will not punish them for protecting themselves and their personal boundaries. No matter what age.
And of course they will make mistakes, that's a never ending part of life.
But if there are never any real consequences for their actions (especially those that affect or hurt others), how are they supposed to learn to treat people (and themselves) respectfully in the years to come?
It doesn't matter how young they are, discipline - in whatever form you feel is right for your family, as soon as they can understand - is so important.