People are constantly using the concept of free speech inappropriately. There is no law that says that anyone can say whatever they want anytime or place they want. The first amendment is only in reference to the government not being able to censor you.
"Free Speech" doesn't mean that a website can't censor you, or that you can't get fired at work for something you say. TFS can edit or delete posts you've made as they see fit, and be completely within their rights. If you said something that the company you work for feels is bad for their image, they can fire you for it, and no one can stop them for that, regardless of the subject matter.
The first amendment would apply if, for example, the government were to try to shut down a publication because of the content they post, the way they do in China. If you are a student at a public school (government funded), the school can be sued based on the first amendment if they attempt to suppress the students' views, opinions or beliefs, or creative expression. If you go to a private school, you cannot sue them for those reasons, as they have no connection to the government.
This has been bugging me for a while, because people throw this concept around like they are entitled to blab their mouths off anytime they please and no one can stop them. Yes, you can be censored, just not by the US Government. But hey, if you don't like the website you're on censoring you, you have every right to start your own, and no one can shut it down. If you don't like the company you work for censoring you, you can start your own, and no one can censor your company. THAT is free speech.