Because once again, xkcd says a necessary thing that people need pounded into their head.
Counter-PSA:
The legal right to freedom of speech (as seen in the first amendment) and the ethical principle of freedom of speech
are different things. I cannot speak for Fred, but any argument I make in this thread refers to the latter and not the former.
The legal right to freedom of speech varies by jurisdiction and changes over time. It speaks of what is in fact the law and not what the law should be. As far as I know, the NBA was perfectly within their legal rights to invoke its bylaws or whatever else (but maybe it wasn't, I'm not a lawyer). That doesn't answer the question "Should people be punished for their opinions?", only "To what extent does the law allow me to punish people for their opinions"?
The ethical principle of freedom of speech, on the other hand, is the idea that we should allow people to freely express their opinions even when we don't like them, and that differences in opinion should be answered with discussion, not force (a somewhat ambiguous term, admittedly). The idea that we should allow speech we disagree with is a recognition of the fact that often in history, ideas we now recognise as good were thought to be disgusting or heretical or ridiculous, and by punishing those that voiced them rather than allowing them to speak freely we held our civilization back. At least, that's why I think it's important, I'm sure plenty of people find other reasons for it. Not the point.
Here's the thing: I personally want to live in a society that upholds the ethical principle of free speech. Partly because I have some unpopular opinions myself, partly because I know I'm not right about everything and if there's some opinion I currently find ridiculous but turns out to be correct I'd like to hear about it. "The government can't arrest you" is not enough, it's the bare minimum. If I will fired from my job for publicly stating X, and I need a job to survive, then probably I'm not going to say X. Maybe you don't think that's freedom of speech, maybe you do, but regardless of what you call it that's not a position I want to be in. And the price I have to pay for that is that I should also allow other people to say X and not be fired (and protest when that does happen, and fight so that it doesn't happen again). You can't just protect "free speech, except for those opinions I find too objectionable". Because then, the people who hold those opinions defend their own right to free speech but not my own, and then you end up in a world where who is allowed to speak depends on which opinions have enough supporters.
To have free speech, you need to have freedom from at least some consequences. The obvious stuff is not being burned at the stake as a heretic or sent to prison in Siberia. But there's also stuff that can limit your free speech without being acted on by the government, like being attacked on the street or refused service at every store in town or being fired from your job. I think that's something we should expect from a civilized society. You are free to disagree.
Disclaimer the first: I shouldn't need to say this, but I don't think racism is a good idea and don't think "well, I'm legally allowed to say it" is a valid argument.
Disclaimer the second: Throughout this post I may talk about "speech" and "opinions" interchangeably. Of course, not everything you say is an opinion, and any arguments I make are about defending thoughts you actually have, not things like lying under oath, deceptive advertising, false alarms, etc. Restrictions on such things are perfectly reasonable and don't impact freedom of speech.