I will explain it to you
The first amendment was written to prevent the federal government from writing laws that restricted speech. The supreme court added some gotchas later on.
In 1925, the first amendment was incorporated
http://en.wikipedia.org/wiki/Incorporation_of_the_Bill_of_Rights#Amendment_I
What the means is that now the states couldn't write laws restricting free speech.
So from 1791 to 1925, what you said could get you arrested and sent to prison depending on the state you lived in.
For the past couple of decades, we can say what we want and not worry about being arrested(as long as you don't run afoul of Supreme court rulings)
http://en.wikipedia.org/wiki/List_of_United_States_Supreme_Court_cases_involving_the_First_Amendment
This Duck Dynasty guy made some statements that caused some butthurt.
He has every right to express his views and he does not have to worry about being arrested or charged with a crime.
That's a great thing
This is an international forum and many posters live in countries where public statements or verbally expressing beliefs can get them locked up.
Our laws protect our ability to speak out mind.
The freedom to speak your mind does not protect the speaker from ridicule, public condemnation and termination of employment (unless that employer happens to be the Government or an entity that falls under federal\state umbrella...but that gets complicated and is not related to Mr Duck)
Mr Duck's employer is not a federal entity nor is it a state entity therefore they are under no legal obligation to respect the first amendment. The only legal obligation being mr Duck and his employer are explicitly defined laws that typically fall under the labor law and the legally binding employment contract signed by both parties.
The first amendment does not protect you from "retaliation"
If you say "Gays suck". Someone can say "Your fathers cock"
If you scream "Gays should be shot", unless there is a reasonable expectation that your words will result in gays being shot you can say that. However, that does not protect your Governor from calling you a brain dead moron.
If there is reasonable expectation that your words carry enough weight that will result in someone shooting gays, you potentially crossed the line.