Too small or too big for what? I don't understand the argument as the metric system is, in my opinion, of the more useful outcomes of the French Revolution. The fact that American scientists generally use the metric system speaks volumes.
The basic size of metric units was arbitrarily determined is what he means. It's not that multiples of 10 is a bad idea, it's that the basic sizes just don't "feel" right.
I remember the attempt to adopt the Metric System back in the 70's but NFL wouldn't hear of it.