A very logical question arises after reading Perek 13 Pesukim 12-13 in Parashat Tazria. The Torah explains that when one’s entire body is covered in Tzaraat "from their head until their feet," they are Tahor, spiritually pure. However, as soon as fresh, healthy skin appears, the person is declared Tamei, impure, by the Kohen. One could ask: logically, shouldn't it be the other way around? Shouldn't the one whose Tzaraat heals become Tahor and one who’s fully covered in Tzaraat be Tamei?
The Gelilei Zahav explains the reason for this puzzling law. He explains that one who has Tzaraat is quarantined so that other people don't "catch the bug" that he is afflicted with. Chazal explain that the “bug” referred to here is the slander and gossip for which the individual is punished. The person is quarantined so that other people don't act like him and speak gossip. One who has Tzaraat covering his entire body is not likely to influence anybody, since they will see his Tzaraat and will not follow in his path, fearing that the same fate will befall them. Therefore, one afflicted with Tzaraat on his entire body is considered spiritually pure and is not quarantined. However, one whose Tzaraat is beginning to disappear is more likely to entice another into speaking slander because the former Tzaraat is less noticeable.
This sheds light on age old advice: people have an easier time of avoiding obvious evil than they do avoiding subtle negativity. It is much easier to steer clear of the advice of the person with full body Tzaraat then that of the person with barely noticeable patches of Tzaraat.