The Gemara discusses a series of rabbinic decrees, which added additional levels of impurity to a variety of objects:

Rava said: But weren’t both decrees issued on the same day? As we learned in a mishna: The impurity of a Torah scroll and other sacred scrolls, and the impurity of hands that were not washed or immersed, and the impurity of one who immersed himself during that day, and the impurity of foods and vessels that became impure by contact with impure liquids, all these are included in the eighteen matters with regard to which decrees were issued on the same day.

אָמַר רָבָא: וְהָא תַּרְוַיְיהוּ בּוֹ בַּיּוֹם גָּזְרוּ, דִּתְנַן: הַסֵּפֶר וְהַיָּדַיִם וְהַטְּבוּל יוֹם וְהָאוֹכָלִין וְהַכֵּלִים שֶׁנִּטְמְאוּ בְּמַשְׁקִין!

One of the oddest decrees was declaring holy scrolls to be impure.  Would that not seem counterintuitive?

The Gemara (Shabbos 14a) explains that the common folk would make the following appraisal:  “Terumah food is holy and scripture are holy, so why not store them together?”  The problem with such reasoning is that the mice would come and gnaw at the food and also gnaw at the scrolls.  Therefore the rabbis declared that the scrolls are impure so that the people would keep their Terumah separate form the scrolls.

This is still difficult to understand, because why could the rabbis not make a Public Service announcement, informing people that it was a bad idea to store the food next to the Scrolls.?   from here we see that the common folk lacked trust in the rabbinic establishment and were resistant to direction from them.  Yet, despite their mistrust and resistance, they apparently had certain hard-and-fast customs that the rabbis could use to influence them.  In particular, they were very careful with certain kinds of impurity and preserving certain kinds of holiness. for example, a bandit, who has no qualms robbing and murdering, will not want to transgress the boundary of defiling Terumah. (At least in the Talmud, there is honor among thieves! See Mishna Nedarim 3:4, Bartenura ad loc.)  Therefore, the rabbis used the boogeyman of declaring the Scrolls to be impure in order to induce the common folk to separate their Terumah from their scripture.  

Another startling example of the way in which the rabbis use the boogeyman of impurity in order to enact various helpful social control comes in regard to, of all things, sexual abuse prevention. You can imagine, if in modern times we have difficulty discussing sexual abuse in public, in ancient times where people's patterns of speech and behavior were far more modest it was even more difficult. Yet, the rabbis were apparently sophisticated and understood the dangers, at least the dangers they knew of in their times. Let us take a look at this fascinating discussion in Gemara Shabbos (17b):

אָמַר רַב נַחְמָן בַּר יִצְחָק: גָּזְרוּ עַל תִּינוֹק גּוֹי שֶׁמְטַמֵּא בְּזִיבָה, שֶׁלֹּא יְהֵא תִּינוֹק יִשְׂרָאֵל רָגִיל אֶצְלוֹ בְּמִשְׁכַּב זָכוּר

Rav Naḥman bar Yitzḥak said: They issued a decree on a gentile baby, according him the legal status that he transmits impurity as one with the legal status of a great zav, who experienced three emissions, even though he did not experience an emission. This was in order to distance Jewish children from gentile children so that a Jewish boy should not be accustomed to be with a gentile in homosexual relations.

Just as the previous case, we might ask why would the rabbis go to such lengths to protect Jewish children, why not warn parents about the dangers of sex abuse? Once again apparently the common folk could not believe, tolerate or accept that their lovely neighbors could molest their children. The rabbis took the boogeyman of impurity, which somehow people felt more fearful of than sex abuse, and this was their way to protect the children.

What do we need to do nowadays to protect our children?