Sorry, one of the ZebraCats went in for an affectionate headbutt & I hit post by accident...
As I was saying, wee folk need corralling in cafés etc full stop to stop their being baptised with scalding liquids. Or getting fingers trapped in things. Or being smacked on the head when someone pushes their chair back not expecting there to be a child sitting on the floor behind them. As well as protecting children from harm, other customers have the right not to be bothered by random small humans.
In this specific case there was a particular person (& dog) that the parent should have been vigilant about keeping her offspring away from given the earlier behaviour. But for some reason she felt it appropriate to let him go & bother them again. She's lucky that it was just a pseudo-ursine execution that was the outcome: if McWuffins The Destroyer had decided the wee lad wanted to play & had bounced up & knocked him down, the boy might have been hurt &/or frightened.
Throwing toys from prams has consequences - they might end up run over or on the train tracks or McWuffined... or sitting on Snowy Owl's lap for the next 10 minutes of Mass because dolly doesn't like to be thrown on the floor, the priest doesn't like you to throw her & you were told that would happen if you threw dolly again. (First time dolly was dropped accidentally. We then had two deliberate lobs, one of which almost made it to the sanctuary - small person in question being in double buggy parked beside Brownie pew at front of nave as is where there's space for wheelchairs or in this case a double pushchair - & as I couldn't be leaping up & down all of Mass & leaving it on the floor wasn't a plan, there was a warning. Lots of adults don't follow through on threats, of course, so my new wee friend thought she'd do some boundary-testing. And of course discovered that I'd meant exactly what I said. When dolly was returned she even got an apology... mother in that instance even thanked me for putting a stop to dollscus situation, though obviously there is a difference between brief confiscation & decapitation 
)
I think it's v sweet you've made that donation on behalf of McWuffins The Destroyer. I'm very much a cat person but he looks adorable. I was knocked down & pinned to the ground by a spaniel when we were in the Channel Islands when I was 5 - literally from nowhere. We were walking along a road & from a lane that joined onto it this dog suddenly bounded out, barking wildly, and knocked me flat. It felt like forever before my DF could get the dog off me & I even when he did I couldn't move as I was totally winded so the dog was still trying to get back to me, barks now interspersed with whines (because of course it had gone from "hello hello HELLO LET'S PLAY LITTLE HUMAN!" to "why is the little human on the floor? why is it making those noises? SOMETHING IS WRONG WITH THE LITTLE HUMAN". When the owner strolled up they did the whole "oh she just wanted to play thing" & of course I know now that she did. At 5 I was convinced I was going to be eaten. I also know now that due to my disability I produce too much adrenaline. So a dog barking doesn't just startle me a bit, it will amp up my fight-or-flight to a ridiculous degree - my body/brain responding as it would to an actual threat. The good thing is that just knowing that's what's going on can help me manage my response... So yes, I'm certainly not all "let me immediately side with the dog[owner]s. But certainly in this case YWNBUAA.