Sigh, I ignored this the first time around.
First, Mr. Eschbach, if everything you said about your experience with that property management company was true then that is your defense your lawyer should use. Prove what you said is true and your lawyer might even be able to counter-sue on a number of grounds.
Having said all that, I'd like to help you clear up a misconception you seem to have. You are not alone, your misconception is shared by many, if not most, of the people in this country.
Free Speech Rights
The first Amendment protects political speech, more pointedly, unpopular political speech. Popular speech needs no protection by definition.
You absolutely do not have the right to harass others when exercising your free speech rights. Also, the right to speak does not extend to be the right to be heard. In other words, you have the right to get up on your soap box in Times Square and rant away about how the "guvment dun you wrong" but you do not have the right to try to force anyone to listen to you. In fact, they are free to talk over you with their own dissertation of how the "guvment did them right" even while you are speaking, if they want to do so.
If everything is as you describe, this is not a first amendment issue. This is a tort issue. They claim you said or wrote something that caused them economic harm. Prove what you said or wrote is true or that they didn't really suffer any harm and you are protected. Given what you wrote here, I think you are going to have a hard time proving you didn't intend to cause them economic harm.
You asked for recommendations. I actually have two.
First, quit trying to try this case in a public forum.
Second, find and retain a good lawyer familiar with defamation and slander defenses.