> Deflation will destabilize the economy if there is massive borrowing, and since most Western government owe about 100 % of GDP, they will prevent deflation for the very reasons you describe. But the middle class should embrace deflation and so should the general economy as it encourages savings which encourages investments which is where the growth in productivity comes from.
You're right. Deflation is not always a bad thing. But runaway deflation is. And runaway deflation is especially likely when there is no increased productivity (like their was in the period you mention) combined with massive debts (which didn't exist in the period you mention, because there was not fractional reserve banking like we have now and value of currencies where intrinsically backed by scarcity of gold).
A little deflation shouldn't be bad for a healthy economy with "sound money", but as you describe yourself: that's not what we're working with here.
It's not just governments who have massive amounts of debt. It's also large businesses and most real estate owners. The middle class should definitely not embrace deflation right now, because deflation could very quickly spiral into runaway deflation.
Runaway deflation = lower wages, lower housing prices, less government budget (less absolute taxes coming in). Less government budget = greater inequality, worse educational quality, leading to decrease in productivity, more crime, more corruption, more waste of resources and aside from government issues: less investments by companies, lower stock market prices, insufficient pension fund reserves due to investments going down (= lower pensions), people losing their house (lower wage = some people can't afford payments on house credit and are foreclosed), housing prices going down more because of foreclosures and bad economy, people increasingly start selling their house at an increasing loss, housing prices go down further, more people start losing and so on.
End result: Japan. Or perhaps worse: the 1930's crash (a prime example of runaway deflation), subsequent poverty, social unrest and wars.
I feel this is not a great explanation though, perhaps someone else can do better.