Yes, but that criticism was not the basis of the argument he responded to, which he perfectly addressed. Try to think of a way to define a unit of measurement that isn't either volatile or completely arbitrary.
Besides, I think that the really useful part of the metric system is that the metric prefixes intuitively make sense when expressed in decimal, and it's clearly expressed from, say, 100143.796 meters, how many millimeters, centimeters, decimeters, meters and kilometers it is. You could say the same thing about inches, feet, yards and miles, but usually I see a combination of those units of varying ratios rather than kiloyards or megainches.
And yet base 10 is pretty arbitrary. It's not just tied to human anatomy, it's tied to a particular non-universal way of interpreting human anatomy.
Granted, I don't really care much one way or the other -- I think metric is more useful for scientific/mathematical/engineering/etc. applications and some of the old imperial units are more useful for things like cooking, and tend to recommend people use whatever's most practical for their task -- but it's hard to escape the impression that metric is an arbitrary system trying to retrofit claims of non-arbitrariness.
I think that you are missing my point. I'm saying that not being arbitrary is too much to ask for from a practically useful system of measure, but what the metric system has going for it is that it is at least consistent with itself.
> but it's hard to escape the impression that metric is an arbitrary system trying to retrofit claims of non-arbitrariness.
I'd like to see any of these claims of non-arbitrariness. I have managed to escape them. The point of redefining the unit in terms of some universal constant is not to avoid arbitrariness but to avoid the inherent volatility of defining it in terms of something which is not constant and not easily reproducible outside earth. No one is arguing that 1/29979245 isn't a completely arbitrary number.
Besides, I think that the really useful part of the metric system is that the metric prefixes intuitively make sense when expressed in decimal, and it's clearly expressed from, say, 100143.796 meters, how many millimeters, centimeters, decimeters, meters and kilometers it is. You could say the same thing about inches, feet, yards and miles, but usually I see a combination of those units of varying ratios rather than kiloyards or megainches.