When was the last time someone shouted "FIRE!" in a theater? Every time freedom of speech is discussed online, it seems like a race for this point to be brought up. Why the obsession?
This actually dates back to a 1919 Supreme Court ruling, and has been used as a "precedent" for countless proposed free speech restrictions, from both sides of the aisle. It's being used to broadly argue that some speech is simply too dangerous, and as such it is acceptable to silence and punish those who use inflammatory language. This argument too broadly applies this precedent, as such movements are often no longer an attempt to protect people and society from the consequences of such speech. Interestingly, it's not a precedent at all, since Oliver Wendell Holmes, who initially made this argument turned his back on his own words as being too restrictive on free speech. The Supreme Court threw out this precedent back in 1969.
The "fire in a public space" argument is used ala carte, as an all-purpose excuse to demand limits on free speech. If anything, we should be far less restrictive on free speech. I'm an absolutist in that regard. In fact, I think the "fire in a public space" argument should be used as a case-study in how facts and arguments can be twisted by those who wish to have a legitimate-sounding excuse. Any legitimate effort to study the initial wording of the original case will find that Holmes' words have been repeatedly misquoted and distorted.
In summary:
1: The "fire in a public space" argument has been distorted from its original usage beyond recognition
2: The original justice who wrote the opinion on the 1919 case reversed his opinion in a later case
3: This has not been the law in the US for almost fifty years.
4: The comparison of what MadJack said to a "fire in a public space" is a comparison which is incorrect.