Inflation can frontload a little demand as you state as people try to buy before prices rise, but it's an overall net negative for an economy as more people can't afford the goods in question moving forward.

Another way to look at the inflation vs deflation argument:

If a currency is inflating, the goods it can buy are becoming worth more and more every day. Why would anyone have any incentive to trade goods that are going UP in value for fiat which is going DOWN in value? On the flip side, if a currency is deflating, there is strong incentive to trade goods for it in order to obtain and hold it. So businesses would be wise to move their inventory and hold their earnings.

Inflation can frontload a little bit of demand because people will think they should buy before prices go up. This much is true. But on the whole it depresses demand. Even if a few more people buy washing machines a little sooner, on the whole, fewer people will be able to afford and buy washing machines going forward.

A modestly deflating currency, which Bitcoin will be, once it comes into its own and is used more widely, is the best possible platform for economic growth. Inflation is only good for the person who is the beneficiary of the created money; for everyone else, and economy as a whole, it's a net negative.