This is not true. Investment will always be made as long as the expected risk/return is better than the rate of inflation. That holds true even if the rate is negative (deflation).
Inflation @ 3% example. O1: Invest at -1% after inflation O2: Do nothing ** Deflation @ 3% example O1: Invest at -1% after deflation O2: do nothing ** Inflation drives bad investment.
Even if the risk/return is worse than inflation investment will be made - as long as it's not a more-negative risk/return than inflation. Deflation sets a positive return for nothing.