"Most public movements only postpone what they protest against -- the labor movement stands as a classic case."The 8-hour work day[1], the existence of overtime pay[2], workplace health and safety standards[3], child labor laws[4], the right to strike[5] and organize (as curtailed as these have become in recent decades) and many other labor laws in the US (not to mention Europe) would provide counterarguments.
"From a scientific standpoint, we cannot say whether these movements were causes or effects."
The causation is usually quite clear, if you educate yourself as to what happened during these movements.
Much of America saw segregation[6] as the natural order of the world and couldn't imagine that people of different races could or should "intermix". Many very powerful segregation proponents fought tooth and claw to keep it alive, killing, torturing, and imprisoning countless people that they saw as their enemies.
If it weren't for the Civil Rights[7] movement, segregation probably would have continued for many more decades, and I would surprised if people of different races could sit in the same restaurants or marry one another in the US by the turn of the 21st century.
The heart of the Free Speech[8] movement was in the Bay Area, so I would like to hope that those HN members that hail from Silicon Valley or SF shouldn't need to have its history recapped for them, so I'll just say that the University of California had dug in its heels against giving in to any of the students' demands, and were it not for their massive and persuasive protests, there's no evidence that it would have been achieved without the movement.
Some decades later, a similar set of events lead to the appointment of the first Deaf President at Gaulladet.[9]
The end of Apartheid[10] in South Africa: due to a mass movement against it.
The independence of India[11] (and many others) was the result of a mass movement.
Those who already know the history of these movements must forgive me for such obvious and superfluous citations. I only do so because I fear that the only way off-hand claims of the ineffectiveness of such movements could be taken seriously is if one had a profound ignorance of history (for which the citations could hopefully make a little self-education easier, for those of a curious mind), or a deep ideological opposition to them -- which I'm afraid no citations are likely to cure.
You say, "As to the labor movement, historically it described an arc between ineffectiveness and corruption -- between a promise of a solution, to becoming a bigger problem than the issue it claimed to address."
Who other than bitter ideological opponents would describe it as such?
I'm sure many American conservatives and "pro-business" proponents see having their employees work shorter days, having to pay pesky overtime pay and compensate them for on-the-job injuries as "a bigger problem than the issue they claim to address".
I've also seen similar criticisms from Marxists who think anything short of bloody revolution is a weak compromise that only perpetuates capitalism.
These are not exactly "scientific standpoints", to use your term, but ideological ones. And I'd be interested to see a source for them other than the likes of the Free Republic or the Nation.
You also say, "As to free speech -- well, I see this as a classic example of modern government's basic strategy, which is to find out what people are going to do anyway, order them to do it, then try to take credit for the outcome."
Look at the history of the Free Speech movement. The students involved in those protests weren't ordered by the government to protest. Quite the contrary, they were bloodily opposed every step of the way. So I'm not sure what makes you say otherwise.
Of course, success has a million fathers and failure none. So it's no surprise that everyone would try to take credit for it now. But I'm not sure how this is supposed to discredit the original movement itself.
Please enlighten me.
[1] - https://en.wikipedia.org/wiki/Eight-hour_day
[2] - https://en.wikipedia.org/wiki/Overtime
[3] - https://en.wikipedia.org/wiki/Occupational_safety_and_health
[4] - https://en.wikipedia.org/wiki/Child_labour
[5] - https://en.wikipedia.org/wiki/Strike_action
[6] - https://en.wikipedia.org/wiki/Racial_segregation_in_the_Unit...
[7] - https://en.wikipedia.org/wiki/African-American_Civil_Rights_...
[8] - https://en.wikipedia.org/wiki/Free_Speech_Movement
[9] - https://en.wikipedia.org/wiki/Deaf_President_Now
[10] - https://en.wikipedia.org/wiki/Apartheid
[11] - https://en.wikipedia.org/wiki/Indian_independence_movement