I don't see any particular difference between saying something on Facebook and saying it to the faces of your friends and family.
"Free speech" was never meant to be utterly, totally, consequence-free. It meant the government couldn't lock you up for saying they stink. If you say the same thing to your boss, s/he's entitled to fire you. If you say it to your friends, they are entitled to consider you an ex-friend.
If you talk like a jerk, whether it be face-to-face, in print or online, people will often conclude that you are, indeed, a jerk.
Further, it is not an infringement on free speech for someone to offer a counter-argument (although it may not make for a quiet life). This is often heard on some of the other boards I read:
Person A - "Leader X is really a Martian!"
Person B - "Um, no, he's not, and here are reasons why...."
Person A - "Help, I'm being oppressed! My right to free speech is being infringed!"
Person B - "How?"
Person A - "Freedom of speech means that you can't say I'm wrong!"