Chazal tell us that after matan torah and before the cheyt ha-egel, people were no longer supposed to die but as a result of the sin people had to die once again.
But why do members of Shevet Levi die? They weren't involved in the sin, and morever, they "disposed" of those who were [see Vi-zos Habracha 1, 9]...? The answer is that EVERYBODY was affected by the sin - even its strongest opponents.
Rav Hunter, in a letter from 1966, says that in our genration, the sin that affects us all is the lack of tzniyus [I use modest language...]. We may rail against it, and we don't watch TV or movies or read inappropriate literature but we are all still affected by the filth, whether we are cognizant of it or not.
Today makes 1966 look like New Square by comparison. We are all affected by the shmutz and all we can do is try to be as pure as possible and learn the topics germane to matters of kedusha.