What a ridiculous comparison. As anyone who has skateboarded ever in their life knows, a bicycle is a thousand times safer and easier to control. Why don't you address the parent's points - that it is impossible to provide safe and effective braking on a skateboard.
It's impossible to prove, but replace bicycles with skateboards and the fatality rate would shoot up.
This product is unlikely to ever replace bicycles. It will always require significantly more skill and practice to ride a skateboard - powered or not.
However, that's an unnecessary measure of success. The board just has to find a big enough customer base to be profitable. There's room in the world for many different kinds of transportation.
As for legality - certainly there are concerns, but unlike the segway, this board is subtle enough to fly under the radar for a while.
It's impossible to prove, but replace bicycles with skateboards and the fatality rate would shoot up.