I'd say you are changing topics. The topic at hand is about devices that are designed to be insecure, because the involved parties just don't care. The manufacturer KNOWS yet doesn't care because the issue doesn't cause him any harm, and the user just doesn't know.
We are talking about devices that willingly expose themselves to the internet (oftentimes without any valid reason to), that are all factory-setup with the same credentials (and no must-change on first use policy), etc.. This is just malpractice, not 0-day vulnerabilities.
Bottom line, vigilantism has a cost and picking and choosing morality of ideals based on your sole opinion is neither appropriate or legal. laws exist for a reason.
Instead of just close/lock the door for my neighbor or call the cop, I use a bulldozer to level the house to the ground. (zero out the flash.)
In theory, the "vigilante" can offer his service to device manufacturer to help remotely clean/update the devices instead of just simply wiping them off the net.
This is where your analogy breaks. Who is your neighbor on the internet? The most logical answer I have is "Everyone with a public IP".
Next, who is the internet police? Sorry folks, there isn't one. If my neighbors house is open, I would call the cops for two reasons. First I don't want to see their stuff damaged. But also, it creates a public nuisance. Some variant of criminals (say drug users or stupid teens) could take up residence in their house, possibly even burning it down, which would make it a direct threat to me.
And that's the problem with our current internet police. They will gladly try to arrest you for breaking into someones house. But they will not bust the 100,000 houses that leave their front door open inviting crime into the neighborhood.
EDIT* I agree with the bulldozer analogy.
While you have raised some valid issues, this is not one of them. Having an unsecured device on the internet has some very definite adverse side-effects.
What do you do when I change my logic to, well this is a ZERO DAY exploit, but you need to be patched, without understanding the complexities of your device or network. Which we all know QA takes a while because of variables. Look at any microsoft patch for evidence of that. Your argument makes it seem like if I decide to weaponize the Shadow Brokers toolkit to lockdown and secure networks around the globe, i'm ok because my intentions are good and manufacturers should have secure code without 0 days. What happens when a proprietary driver or component fails because of a change made to the kernel or the way it handles driver functionality? Now I've broken / disabled something because I didn't know the intricacies and instead chose to do what I thought was right.
"No good deed goes unpunished"