"dangerous pieces of technology"?
I will agree that MP3 players can be misused. People can insulate themselves from their surroundings to the point where they are unaware of threats or danger to themselves or others. They can isolate people emotionally. It is certainly easier to listen to music which is predictable than to deal with real people where the listener has no control over the interaction. However, I don't think most people abuse them. In my experience, most people have the courtesy to turn them off while interacting with other people or the good sense to turn them off when their activity requires special vigilance
Their insulation value can be helpful at work where it's more productive to have familiar favorite music playing than to listen to nattering coworkers. If you have one that records, it's useful for recording events (e.g. lectures) for yourself or for others to listen to or review later.
If you're healthy enough to exercise (I'm not, unfortunately), it's good to have your favorite tunes to keep you company while doing what is an inherently boring activity.
Music and art are things which enrich our lives. I have "inner resources" but I will never compose great music or art. I play a couple of instruments, but I'm no virtuoso. I can recall and replay favorite music in my mind, but it's not as satisfying as a great performance.
This leads to the discussion of recorded versus live music... Even if you live somewhere which provides access to high-quality live performances (many people don't), concerts are expensive and unappealing to anyone with any degree of social anxiety.
In short, while some of your criticism have a basis in fact, I think many are overblown, overstated, or stated as facts when they're really only your opinions. Portable MP3 players are not inherently evil. Neither are people who listen to recorded music somehow mentally deficient. I know both certifiable morons and Mensa members with portable MP3 players. As with computers, there's no qualifying test to purchase one.