1) Cutting your marketing budget in a slow period will only help conserve profits in the short term.
2) Ultimately the brand will emerge from the downturn weaker and much less profitable.
3) It is better to maintain share of voice (SOV) during a downturn. The longer term improvement in profitability is likely to greatly outweight the short term profit reduction.
4) If your cometitors are cutting their marketing budget the longer term benefit of maintaining share of voice will be even greater.