This is their way of making "conscience matters" into real sins. You go ahead and get some eggnog, and you are going to have Brother Hounder accosting you for "worshiping the sun". When you explain that you are getting the stuff because you happen to like it, without regard for the holiday, they tell you that you are stumbling others--even if there are no other witlesses in the store besides you and the hounder who barged on you. The same goes for the Easter candy.
Or, you happen to like a song that is "questionable". The record is inconspicuously stored at home, and the song is in your MP3 player (which itself is inconspicuous). The volume is low enough so the music stays with you. However, the hounder now comes in and hunts through your music collection. Sure enough, that record comes up (even though the hounder had to look several times). Now, you are stumbling anyone that comes into the cancer by having that record (not even in plain sight) at home.
I think there should be a concept of "private property". The humanoid that dragged me into the cancer had several records in his own collection, and I never got to see all of them (nor was it even my business); yet he is going to tell me to get rid of my records that he doesn't approve of to avoid stumbling others. They are put away, inconspicuous (you can tell that there were quite a few, but reading the labels was difficult unless you know where to look for them). I have seen almost no other witlesses' record collections (and, when I did see them, I viewed it more as a parental control issue rather than a stumbling issue). If adults had "bad" songs in their private collection and the albums were not flamboyantly displayed, it was none of my damn business.