These things really can destroy cases as a lot of stuff suddenly becomes inadmissible in court because it wasn't presented through proper channels and jurists may be requested to ignore it entirely. At least this is how it can work in the USA in a lot of cases.
Further, depending on the circumstances of how the initial connection to the pedophile in question was made, it can be potentially considered a type of entrapment, as it may be able to be argued that if this person did not present themselves as a willing child to begin with that the perpetrator may have never attempted to pursue such a crime.
The fact that they're backed by right wing politicians kind of says everything: They're way more concerned with looking like they're doing something about the social issue of pedophiles while actually not doing very much at all. There's also a suspiciously high number of people in these "catch a pedophile" groups who end up being convicted of some sort of pedophilia themselves, as though they're projecting their own disgust with themselves and/or they think people won't suspect them of it as long as they're busy busting others for it. The conservative right wing only cares about appearances, not real solutions, while allowing the Epstein class to continue trafficking, raping, and killing children.