The "marketplace of ideas" meme (along with many of what Americans consider to be First Amendment Free Speech protections) came into jurispridence in a 1919 dissent by Oliver Wendell Holmes in Abrams v. United States in which Holmes defended free speech rights based on the "marketplace of ideas" concept proposed by among others John Stuart Mill. Who was distinctly tardy to the Founding Fathers table.

There's a brief article on the particulars here:

http://scholarship.law.duke.edu/cgi/viewcontent.cgi?article=... (PDF)

There's a longer treatment in Thomas Healy's The Great Dissent.

http://www.worldcat.org/title/great-dissent-how-oliver-wende...

The concepts are curiously intermingled with much of the reformulation and representation of Adam Smith's ideas which took place over the 20th century, also generally misunderstood by the lay public thanks to an aggressive 60+ year marketing campaign by the Mont Pelerin Society and Atlas Network. But that's another rant.

The time of Galileo and his troubles was further away from the time of the constitutional convention than the Civil War is from us.

i.e not e.g.

Galileo's troubles as you call them, was an example of false speech the new Government wanted to protect and be allowed to enter the marketplace of ideas. Moreover, I was not suggesting Galileo was the reason for the 1st Amendment.

Also, I am not exactly sure what the distance of the Civil War to today has to do with the distance of time from the drafting of the Constitution and Galileo. Seeing as the Founding Father's modeled the new Government off of the Roman Republic (509BC-27BC), they were more than capable of applying more modern history lessons taught by the Catholic Church and Royal Crown which they wished to avoid repeating.