

Some of these “pedo hunter” groups have attacked completely innocent people where the accusation of someone being a pedo was completely unsubstantiated. This is the problem with monetizing vigilantism: It creates a demand, and if that demand is not being met by a supply of actual criminals, then it will be filled by vigilantes criminalizing innocent people.
You are working under the assumption that these “pedo hunter” groups are all acting in good faith and on good information. I encourage you to do some reading. There are many cases where these groups pretend to be 18 year olds, lure an unsuspecting person into a meeting, and then lie to their audience about the age they originally claimed to be online, as Xatolos has pointed out.
Lots of them do it to lure in and attack LGBTQ+ folks, while others act on false accusations they receive from third parties:
And I can’t tell you how many times they just straight up confront the wrong person. Here’s one example, and here’s another, here’s one more, and here’s yet another.
These are not professionals. They are YouTubers looking for fame and relying on outrage and violence to get it, and they all-too-often don’t care who gets hurt or killed in the process.