You're simply mistaken.
The metric system is - like the Imperial - completely arbitrary.
The meter is precisely as arbitrary as the foot.
The liter is precisely as arbitrary as the gallon.
The kilogram is equally arbitrary as the pound.
Each of these was a unit of measure selected ex nihilo.
The meter was originally defined to be 0.000001 the distance from the Equator to the North Pole (which it isn't), and then rationalized back to "the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second"
Really? 299,792.458 is pretty arbitrary.
The kilogram/liter is even more amusing: "...as the volume of one kilogram of pure water at 4 ÂC and 760 millimetres of mercury pressure. The kilogram was in turn specified as the mass of a platinum/iridium cylinder held at SÃvres in France and was intended to be of the same mass as the 1 litre of water referred to above. It was subsequently discovered that the cylinder was around 28 parts per million too large and thus, during this time, a litre was about 1.000028 dm3. Additionally, the mass-volume relationship of water (as with any fluid) depends on temperature, pressure, purity, and isotopic uniformity. In 1964, the definition relating the litre to mass was abandoned in favour of the current one."
Hell, the liter isn't even an official SI unit, and the kilogram self-identifies that it's not even a unit - it's 1000 arbitrary units (how inconsistent is that?), with further a 'standard unit' (the ton, 1000kg) that doesn't use the proper prefixture, but an arbitrarily-chosen name.
In fact, one might say that the core fact of the metric system IS its arbitrariness; rather than being analogous to a body part (the foot, or the cubit, for examples), the meter has little to do with anything.
Your point about coherence (CnP from wiki) is absolutely true, however. Which is why the people that use such calculations DO tend to use metric measures.
Then again, for some reason the SI-evangelists DO accept without question or complaint a variety of their own non-decimal systems, such as the calendar, clock, circular measure (angles) and thermometer showing that even to them, apparently decimalization isn't the ne plus ultra after all?
Use the unit of measure you want. Let other people use the units they want.
If you don't like the units they use, and it's THAT BIG a deal to you, don't deal with them.
(And it's pointless to whinge about conversion errors and 'all the disasters' these have caused like the MRO or the Gimli Glider. "Crap" happens all the time, mostly due to sloppy work, and the proportion of such incidents due to metric/Imperial conversions is astonishingly small. Conversions are just a symptom, not a cause.)