Another great anarchoparenting/peaceful parenting article.
I like using the time in technique. We get to calm down together and discuss what lead up to the altercation. Instead of teaching my child that if they upset me, I will isolate them from me, I remind her that I love her and it is the behavior or action that angered or upset me, then I do a self assessment to see if my behavior was at fault, and open things up for discussion. I always offer hugs and snuggles as we discuss what happened and how we can modify our behavior to have a better understanding of each other in the future.
As for tantrums, a lot of parents do not realize that they actually throw tantrums themselves and that their children will also pick up on that behavior. Children love to universalize everything.
My child has never had a tantrum as you have described. We always have a pre-outing talk and, if needed, negotiation. I always look for a win-win. There have been times when I have noticed her becoming frustrated, so we will sit down and see what we can do before it turns into a tantrum. I also have to remember that she is much smaller than I am and for every step I take she is taking two (or three, when she was smaller). If I am getting tired, she is probably close to exhausted. I know I can get a little cranky when I get tired and she is just as human as me.
I also try to keep her involved with what I am doing while shopping, asking her advice and including her in the decision making. I also use it as a learning experience: How to budget, get the best value, practice her mathematics, how sales tax can effect how much we can buy, etc. It makes things a lot of fun for both of us.

I don't know if you are going to touch on this in a later article, but I also sit down with my child periodically and have a parental job review. Since being someone's child is one of the most involuntary relationships you will ever be in, I like to check to see if she did have a choice, would she have chosen me and what I can do to improve her childhood experience with me.

Again, keep up the good work.