I think "free speech" means that you can say what you want in the town square and the modern equivalents, especially when it comes to doing so without government interference. But it doesn't mean you can shout "fire" in a theater, or walk into my house and start spouting off about some BS. Similarly, you can't say whatever you want in a forum that is owned and moderated by private folks who have imposed what many of us think of as reasonable limitations. It probably didn't help that instead of making a constructive point ("Hey, could we post political posts if they are respectful?"), the subject of the post, and almost immediate attacks on anyone who disagreed with you, were probably not well received.
FWIW, I bet there are more people on here who agree with your political views than oppose them, but most members don't feel the need to say so, or they do so in a more respectful and reserved manner.