I didn't say that money supply is the only variable in the equation of exchange. But we need to respect the economic terms for what they are and not mix different categories even if they are in a cause and effect relationship.

Equation of exchange (most popular form): M*V = P*Q

M - money supply (mass of money in circ.)
V - velocity
P - price level
Q - productivity or quantity of product (goods, services)

So if you have a growing economy (Q is rising) and there is no change in the way you do business i.e. trade (V doesn't change) you need to increase the money supply to support this growth. Most prices are downward rigid and this is the only way to make it work. If Q and M are in proportion there is no inflation, just healthy growth supported by growing money supply.

This is all pretty elementary, no differences in opinions between economic theories etc.