Don't. The (programming) world isn't perfect and trying to protect him from anything "confusing" or bad will not help him in the long run. Instead, explain. If you don't have a good answer, research the reasons. Getting to know and working around (or with) the quirks of the system is important. Don't take that away from your son.

Why would you want your own biases get in the way of educating your son? Python is a great first language because it is both approachable and practical. You can go in any direction... webapps, scientific computing, and even games (as I've already suggested).

I learned QBasic when I was 9, when I was 11 and realized the world wasn't developing real applications in QBasic, I was pretty upset and never wrote a line of QBasic ever again. I was pretty bummed at the time, and moved on to C.

There certainly is a reason top universities are moving to Python to teach beginners programming...