My understanding is that everyone agrees that expanding the money supply under conditions of economic growth is necessary to avoid deflation.

The contention centers on whether price deflation is a good or bad thing.

If you're a "grow the pie" kind of person, you probably think that it's a good thing because falling prices without falling demand is simply a sign of the pie having grown.

If you're a "redistribute the pie" kind of person, you understand that deflation is an opportunity to control where newly created wealth is funneled to without the people who create the wealth noticing.