I only read the first page before writing this, but I'll post it anyway, even though things do seem to have gotten out of hand
I must say, I also don't regularly listen to secular music, I play drums to it relatively often, but I do that to build up my talent to be able to honor god more. I'm not afraid of listening to it, I just (personally) have trouble giving god all the honor when I'm listening to someone putting god down in the background.
The important part is 1 Corinthians 8:9: "Be careful, however, that the exercise of your freedom does not become a stumbling block to the weak."
Everyone has a stumbling block. In fact, everyone has loads of them. Listening to secular music may not make you stumble, but if it makes someone else, for example goldenight stumble, you are making yourself accountable for his stumbling when you try to convince him to listen to music he knows in his heart he shouldn't listen to.
In the end, everyone has to know in their heart whether secular music is a stumbling block for them, or if they can use it to honor god. No two people live in the same circumstances.
Next point. If listening to secular music makes goldenight stumble, and he knows in his heart that it's wrong for him personally to, the yes, he is willingly sinning against god when he actively listens to it, and that does open doors to Satan.
Never make yourselves the illusion of being perfectly safe from temptation. We may be under god's protection, and he is stronger than Satan, but we are weak. We fall to temptation again and again, so not until you are in heaven are you entirely safe from Satan.
Just my 2 (or a little more) cents ^^
Not even Christ was safe from temptation (he defeated it, of course, but still), so how could we weakling be in any way safe from satan and demons?