Now we can explain what it says in 'פסוק ג.
"ואני אתן וכו' למען טמא את מקדשי ולחלל את שם קדשי"
And I will set My attention upon that man, and I will cut him off from amidst his people, because he gave of his offspring to Molech in order to defile My holy ones and to profane My holy Name.
In 'פסוק ב we saw in the punishment an allusion to the fact that this sin relates the Klal Yisrael as a whole, now we see this explicitly because this sin involves "וטמא את מקדשי" as Rashi explains "את כנסת ישראל שהיא מקודשת לי" - The Jewish people who are sanctified to Me. This indicates that this sin engenders a contamination of the Jewish people who are holy to Hashem. Just as defiling the Mikdash [טומאת מקדש וקדשיו] is an extremely serious offense, so is defiling the Jewish people by giving one's child over to Molech.
It is also "ולחלל את שם קדשי" - A Chilul Hashem of the GREATEST magnitude. When one causes a Chilul Hashem in front of ten people it is very serious [and one must gives one's life rather than do so - see Sanhedrin 74b and Rambam Yesodei Hatorah Ch. 5] but here is worse because the very sin itself is all about defiling Hashem's name in a public way i.e. this sin inherently relates to the Klal, as we saw. This would explain why the death penalty down here on earth doesn't suffice and it is also necessary to mete out Divine retribution - unlike other sins where one is either punished by the courts or by Hashem but not by both. So we require that he be executed, it be carried out by the Am Ha-aretz [in order to rectify their blemish - the פגם הכלל] and in addition - כרת from Above.
Whoa!!
On that it says in 'פסוקים ד' וה - But if the people of the land ignore that man when he gives of his offspring to Molech, not putting him to death. I will set My attention upon that man, and upon his family, and I will cut him off, and all who stray after him to stray after Molech, from amidst their people. Here is says that that if the "Am Ha-aretz" don't detach themselves from this man and his sin by stoning him, then Hashem will find another Tikkun for the Jewish people [Hashem loves us and wants to fix us]. That is by punishing not only him [with כרת] but his family as well [according to Rashi it means that they will suffer Yisurin because the כרת relates only to the sinner himself - והכרתי אותו]. The family is a microcosm of the Klal. By punishing them it effects a Tikkun for the greater Jewish community. Rashi says that they too are guilty because ".... there is no family in which there is an [unfair] tax collector which may not [be regarded as consisting] entirely of tax collectors, for they all cover up for him." As we said, this moshol could apply to ANY sin. But when it comes to other sins that are not of a communal-Klal-Yisrael-nature, being an accomplice who didn't actually commit the sin is not enough to mandate punishment. But here where the sin is inherently one that relates to the community at large [because it involves a father giving over his son granting it a generational element, as we explained] we don't need much in order to punish the family. The fact that they cover up for him is enough.
As they say in the yeshivos - farentfert aleh kashyes!! [Polish for "this is AWESOME!!"]
[עפ"י תורת מו"ר הגאון הגדול ר' ד"י מן זצ"ל]
BUT THIS IS JUST THE BEGINNING!! HASHEM SHOULD GIVE US THE LIFE AND HEALTH AND FINANCIAL MEANS TO CONTINUE SHEDDING LIGHT ON THIS PARSHA!!
[עפ"י תורת מו"ר הגאון הגדול ר' ד"י מן זצ"ל]
BUT THIS IS JUST THE BEGINNING!! HASHEM SHOULD GIVE US THE LIFE AND HEALTH AND FINANCIAL MEANS TO CONTINUE SHEDDING LIGHT ON THIS PARSHA!!