As much as it galls me to agree with this point I do. Somewhat.
If you apply the OODA loop to a bikejacking scenario the crim is WELL ahead of you by the time you are even aware of the threat. They've observed, orientated, decided and they are busy acting. It's unlikely that you are going to be able to deploy a firearm in time to ward off the attack. In a home invasion scenario hopefully your alarm is on and your doors are locked which will give you a few seconds to catch up.
Add to that the fact that you can only legally use a firearm in self defense if your LIFE is threatened. Maybe you could argue that having a brick thrown at you is life threatening. I don't know.
Concealment is also an issue. Our law states that you must conceal your firearm. Riding with a firearm with a visible silhouette is probably illegal and could possibly make you a target. Riding with it in a backpack is a waste of time IMO.