People always get defensive when talking about this topic for obvious personal reasons, but just think about what the process actually involves.
What makes you think supporters of circumcision don't know "what the process actually involves"?
The fact that they are finding a way to rationalize hacking off the tip of a tiny human being's penis without consent. But you're right: Perhaps I shouldn't similarly rationalize their position by assigning them the benefit of ignorance. Some are just heartless and set in their ways because muh tradition101!