Free speech isn't you being able to say whatever you want, wherever you want.
You're entitled to share your opinion in public, nobody's stopping you to go out in the street and strongly voice your opinion about compagnies asking you to be polite on their plateform. That's free speech.
Saying whatever you want on a privately owned plateform and going against the terms of service you explicity agreed on isn't free speech. And SE taking action to remove you from their plateform isn't silencing you since you're very much still free to speak your mind in public and there's nothing they could do against it.