As humans, we seem to be looking for a pattern of life that doesn't require us to have self-discipline. Many of us are looking for a way to live or a set of rules that doesn't require us to actually walk in discipline in our lives. We take certain things and say "Ok, this is bad!" And it could be taken to the extreme, so we don't want to partake in that because the chance that it could be taken too far is a possibility. An example is as Christians, many of us say secular music is bad. If it's not explicitly about God then it's not God honouring or good. We say secular music can lead to "this" so stay away from it all together. But what if I write a beautiful love song to my fiancée and let her know how amazing I think she is? Is it not God-honouring to use the God-given gift I have to remind the woman I'm gonna marry of how much she means to me? We use a lot of scripture to back it up - what you put in comes out sort of thing. Secular music can lead to other things so stay away from it completely! Yes, there is music that can affect us negatively and we should not let ourselves get caught up in that, but should we really vilify all of it? Do we not trust ourselves to have self-discipline and control what we listen to?
If I don't trust myself or want to discipline myself and not go to the extreme, then I will cut out that thing completely and urge all others to do so too.
Say there is a large chocolate cake. One piece would be ok. It's nice and I'd enjoy it. The whole cake would be bad for me. I'd be sick after eating the entire thing. Eating one piece could possibly lead to me maybe, just maybe, wanting to eat the whole cake. Rather than trusting myself with the responsibility of controlling what I eat, I say that cake is evil! I stay away from it completely and tell everyone around me to keep as far away from it as possible because there is the chance of taking it too far, so it is wrong.
*Continued in the comments...*