What a childish response. You are going to break a child's bubble gun because you don't want a few bubbles blown on you? Think about the lesson you are teaching your own kid. "Son, I don't want bubbles blown on me in Disney World, so I'm going to smash that 3 year old's bubble gun because that will show him who's boss - watch and learn dear."
I have also never seen kids running around Main Street blowing bubbles in strangers faces. I've never seen bubbles there - well, except for in the rides Disney operates. I think people are exaggerating.
Our kids are all grown up now and have kids of their own. Luckily, they grew up in the "Pre-self centered my special snowflake is all that matters in WDW" Era. Never saw such bad parenting in the parks back then. If my kids had trouble waiting in line or at a restaurant, we either gave them a quiet toy to hold or one of us took them for a little walk or bathroom break. If the line was too long, we didn't even bother and went on to something else, as I could make the determination that my kids wouldn't be able to wait for so long. As they got older, they had
RULES-wait in line patiently or don't wait in line at all. YES, just because we were at WDW, our kids still had RULES to follow, as we were well aware that we were sharing our day with thousands of other guests. If they followed all of their rules, they got to pick out a special gift or snack by the end of the day. Simple as that and worked like a charm.

My children now have kids of their own and they follow the same procedures & they are always aware that they are not the only ones in the park & very respectful of those around them.
I have also never seen a kid running around Main St. spraying bubbles. & if I did see it, I really wouldn't care because it's a street and an open space & there is plenty of space for the child to move around and plenty of space for me to move away if I'm bothered. I'm specifically referring to the moron parents who allow their kids to spray bubble guns at people and run all over the place popping bubbles while they are waiting in close quarters to crowds of other guests, like ride lines, parade crowds, fireworks crowds, even on buses & yes, I have seen bratty kids behaving this way in these locations over the years. & when I've politely asked a parent to stop, I'd say more than half of them either respond by purposely ignoring us or responding rudely.
So, you are right, it might be childish to break a bratty child's bubble gun if they are spraying it in my face, but be aware that there are plenty of people out there who would respond like that so you might want to have a back up plan when the bubbles run dry.....here's an idea: SET SOME RULES
You and your children ("you" figuratively-not you literally) are not the only ones sharing space in WDW, especially in crowded quarters. So, if you think it's disrespectful and rude for me to light up my cigarette in line and blow the smoke all over your kids, run around and smear peanut butter all over your peanut allergic kids faces, swear loudly in line or talk about my sexual escapades from the night before (oh my....

), than have the same respect and use the same common sense & common courtesy in line that I have. I couldn't even imagine being so disrespectful toward those around me. It amazes me that some people just have no clue.....or no class....
& again, I'm not referring to the happy little bubble blower who is playing in a wide open space in the parks or in their chairs at a CS restaurant-I'm talking about the moron parents who give their kids these toys in close quarters to others, set no boundaries, and could care less that their kid is bothering everyone around them.