During the Nuremberg trials, it was said of the Nazi war criminals that the farther away from the actual killing they were, the more actual responsibility they bore. Responsibilty stemming from influence is a major theme in the parsha, where chapter 13 lays out in succession three different paths to idolatry and their consequences: false prophecy (navi sheker), the private seducer (mesis/mediach), and the idolatrous city (ir hanidachas).
Each category has unique halachic characteristics. Chizkuni, quoting Sifri and Bechor Shor, asserts that a navi sheker never starts out that way; rather, he will be a once bonafide prophet with proper spiritual credentials who, upon becoming corrupted for whatever reason, will use the same “signs” (os/mofes) for idolatrous purposes that he once utilized for G-dly service.
In the case of mesis/mediach, Rambam in Hilchos Avodas Cochavim 5:3 details how this is the one case in all of Torah/Halacha where legal entrapment is not only permitted, it is encouraged. This follows all of Rashi’s quotes from the Sifri that, whereas in all other capital cases all efforts are to be made to spare the defendant from execution, in this case the opposite pursuit is to be the ultimate end.
The ir hanidachas, of course, is unique in halachic literature (along with the ben sorer u’moreh) that its relevant halachos actually prevented the possibility of it ever being carried out.
What’s the link between all these?
Knowing who and what your influences are and where they are coming from is the strongest common denominator. Specifically, the Torah is warning us that sometimes the worst kind of behaviors happen right in front of our noses and can be perpetrated by the people we love the most and are supposed to admire most, as opposed to the city streets, or “ir”, where we might be less surprised to find widespread moral turpitude. The Torah tells us not only that it can happen here, but that it will.
Regarding the consequences, while it seems that the mandated earth-scorching of ir hanidachas seems to be the most draconian of the three cases, the legal barriers to the punishment ever being carried out actually mitigates that: there comes a point when you simply can’t mete out widespread punishment, even if you should. No such barriers exist in the other two cases. The Torah is directing us to stop the influences in its tracks with extreme prejudice when we see them, before it becomes too late and results in widespread destruction, executed judicially or otherwise.
A tangentially related note: I’m going to go out on a limb here, but one might possibly draw an analog to stories of home and clergical abuse one hears about nowadays; irrespective of their (purported) infrequency, or possibly even because of it, there exists an admonition of sorts to administer the consequences harshly—and publicly. The mishna in Avos that says “Hamechalel shem shamayim ba-seser, nifra’in mimenu be-gilui”—clandestine chilul hashem usually results in a very public payback—may be more than just hinting at this.
Religious communities of all sorts have a built-in aversion to “public washing of dirty laundry”. The Torah indicates that such notions are not necessarily Jewish values.