I really don't see how the principal is any different from that of the Church of the Flying Spaghetti Monster. It's basically using a fictional character to prove a point about religion by applying "moral codes" to its followers within the context of what "deity" has been chosen. It's most often meant to be a hyperbolic satire about Christianity.

The religious and/or spiritual beliefs of a person aren't really any of my business. It's their lives and their choice what to do with them. That doesn't mean I will not have my own OPINION in regards to their beliefs, though, based on my choices and what I believe in. But if someone wants to practice batmanism, then by all means, Dark Knight, don your garb and protect the night.