Everyone keeps debating whether or not the built in deflation is good or bad. But... how does bitcoin have built in deflation? It only has a decreasing rate of

Everyone keeps debating whether or not the built in deflation is good or bad. But... how does bitcoin have built in deflation? It only has a decreasing rate of inflation, which can't go negative (since bitcoins aren't destroyed). So assuming the demand for bitcoins becomes constant, their value will be constant.