Not quite. The "free exchange of ideas" on racism didn't really exist at that time. What changed the attitudes of the past was a relatively small minority of people agitating for change, organizing marches and protests, stating sit-ins and get-out-the-vote campaign, and building up enough momentum to convince elected officials to push through anti-discrimination and anti-segregation legislation, legislation which was actively opposed by the majority in many communities.
Said opposition was very often brutal and bloody, and many people died trying to achieve said equality. Sitting around talking about it didn't do it, people going out and getting themselves killed trying to make a change did.
Racism isn't countered much by "the free exchange of ideas", because there really aren't any ideas to be exchanged from the racist's point of view, there is only emotion and rationalization. What counters racism most strongly is exposure to and interaction with other ethnicities, where one can experience the humanity of others, instead of merely being preached at about it. Racism, despite the justifications given for it, is ultimately based on fear, and only countering that fear with experience and exposure has any real effectiveness.
If you listen to a lot of the former neo-Nazis, those who have turned their back on other hate groups, and embraced a more progressive and less hateful outlook, one of the key factors was circumstances forcing them together with the objects of their hate. Not by "ideas" happening to drift by them while they were ensconced in their echo chambers.
One who did not live through or closely study those times tend to forget that nearly the entirety of American society was an echo chamber of sorts. Very little dissent and free speech was actually tolerated if it countered the jingoism, red-baiting, racist fear-mongering that dominated American culture at the time. The various media production codes, the red-scare witch-hunts, neighbors suspiciously spying on neighbors, and so on. It took work and blood to get to where we are today, not whinging about "free speech" and censorship.
I think what people are failing to understand is that actions like Facebook banning racist, terrorist, and similar group is doing is breaking up those very echo chambers.
The "free exchange of ideas" is only possibly where ideas are exchanged. Social media echo chambers do not allow said free exchange, and those who are engaged in those echo chambers are not about to go seeking out other ideas.
When I was in my 20s, I very nearly ended up going down what we would now call an "Incel" rabbit hole. What prevented me from doing so was having people around who made the effort to call me on my BS, and verbally slap some sense into me; combined with going out and actually spending time with people, women in particular, and learning through experience how and why I was wrong.
If I had had one of the contemporary Incel communities to reinforce my anger and fear, then I very likely would have ended up far, far worse and never gotten myself out of the negative headspace that enabled it.
The same with my Evangelical religious-right upbringing. It was being forced out of that and into a wider society, where I could experience things from outside perspectives, that enabled me to turn my back on it.
That[/i] is why the far-right, religious terrorists, Incels, and other hate groups push so hard against allowing private companies like Facebook and Twitter and Reddit to remove their hate. They rely very heavily on having those echo chambers, having those communities reinforcing their fears and hatreds. They depend on those platforms for recruitment and reinforcement. That is why they have duped others into defending them as "free speech". They are not at all in favour of free speech. If you don't believe me, go hang out in one of these groups, try to "freely exchange" anti-racism, pro-LGBTQ, pro-feminism ideas. See how quickly you're shouted down and banned.
That's why religious groups are pushing so hard right now for "religious freedom" legislation that allows them to divorce themselves, and more importantly their children, from wider society. To create those echo chambers in charter schools, churches, businesses, and so on.
In order to learn and grow and "freely exchange" ideas, the echo chambers need to be broken up. Leaving them to fester and grow will not in any way serve any sort of "free exchange". As long as people are capable of finding sufficient numbers of others to reinforce their fears and hatreds, they are not going to be interested in "ideas" that oppose their own worldview.
