Comments time! Feel free to mock or ignore.
Though I'll note that we should be modest about our claims to the effectiveness of monetary/fiscal/regulatory interventions in the economy. There's only one method to even remotely manage an economy technocratically - monetary policy - and even that eventually can only steer nominal variables (the money supply, prices, inflation, nominal spending, etc), not real ones (specifically, real spending). Fiscal and regulatory policy are only modestly able to tame real business cycles, and the timing is usually hard to get right.
"This time it's different", except that it is and it isn't. There is no perfect policy because there are both samenesses and differences in every situation. So there is to some extent always a play it by ear and react to the situation as it develops. Part of what the Keynesians failed at that resulted in them being discredited was excessive confidence that they had all the answers. But everyone else that did marco had the same failures at some point. Including the laises fairies. You do the best you can with what you have. Sometimes you'll be wrong, but it's pretty much always better than doing nothing.
Further, regulatory and fiscal policy can themselves create business cycles, but that's a discussion for another day.
If you read the discussion above, I never denied it:
Of course they are. Now I'm not going to claim that other factors, government missteps, wars, natural disasters, don't also do so. But financial bubbles and bursts are an inherent part of capitalism. You can't have one without the other. You can only attempt to reign them in and mitigate the damage.
Of course, the business cycle has been found to cause sunspots too...
A decent reference here might be Friedman's "The Methodology of Positive Economics", which isn't the best defense of economics but is good enough for this discussion.
I find the "Oh, that's not proven beyond the least possibility of dispute, therefor it's meaningless and we'll ignore it" response to be singularly lacking in credibility. And that's what I was referring to above. Same thing often heard from climate deniers, smoking risk deniers, pollution cost deniers...
While there's certainly some theoretical validity, it's all too often an excuse for people to go on doing whatever the hell they want without taking responsibility for their actions.
I'm not sure you can make the causal claim that deflation -> depression under a gold standard, but I'm having trouble raising a counterexample. Consider this an "I'll get back to this, if you'd like" marker.
"Strongly associated"

No one has proved this. There is only arbitrary interpretations of history, just like yours here. One could interpret in a million other manners and they would be just as much speculation. There is no scientific value in that.
What's your standard of proof? You can rationalize away and shift the blame all you want. But while it is true that sometimes the government is in the wrong, there's no plausible way to say that there isn't a business cycle caused by, you know, business.
Without knowing facts (person A prefers having money supply manipulated in manner B or doesnt) it is impossible to know. And as those persons arent acting(as it is an externality), it is impossible to know the facts. Speculation.
People express their preferences through choice of government.
Same thing.
You keep making the same methological mistake of using positivism in social sciences. That necessarily means giving up scientific value.
And you don't? You don't have the smallest lick of science behind any of your points. You begin with your conclusions and then look for a way to justify them. You aren't following a scientific method, because evidence is meaningless to you.