Imagine a business man in a lab coat? You're like, "what's wrong with you?", right? It is the same thing with Christianity. There are ethics in which ever field you find yourself. As Christians, we are to represent Christ where ever we are. That is why the bible says we should let our light shine before men that they may see the GOOD works in us and glorify our father in Heaven. Does this dressing glorify God? Which people normally dress this way? If you begin to ask yourself these questions, you'll realize that this kind of dressing is portrayed by rappers, street boys, basically, American bad boy culture. So should we do what the unbelievers do?
There is one thing the devil is good at - re-branding evil into God. In the bible, he did that with an apple. In our days, these things are what he is using to get us off track. One of the fruits of the spirit is gentility. Does goth dressing portray gentility? I don't think so. Let us all be careful