Verbal aggression and physical aggression both have the same root and both have the same effects
It is absurd to assert that calling you a name and punching a fist in your face "have the same effects".
Fortunately, the US Constitution disagrees with you, since "verbal aggression" is protected speech, while physical violence is not.
Freedom of speech applies to identifiable people, to those who are ready to take the heat if they are proven as liars. Not to the so-called "anonymous cowards"
False again. Anonymous speech is legally protected in the US, and for good reason. Anonymous speech is an essential aspect of free speech.
Now, you are entitled to sue my ass and get a large amount of money from my misdemeanor
Libel is not a misdemeanor or a felony. Libel is a civil matter. But in order for something to be libel it needs to be both false and likely to be taken seriously.
Now I, covered by anonimity, go there and write "Shakrai has a small dick, finishes in 2 minutes and can't satisfy a woman ", you wouldn't like it. You could just go ahead and ignore my entry and even the forum altogether, but your co-workers won't.
They'll quickly figure out that the site isn't trustworthy once messages get posted about them, perhaps even by you. That's the thing about anonymous rumor sites: they aren't intrinsically credible.
But sometimes they may get people to notice something that they hadn't noticed before, like Shakrai's string of unsuccessful relationships. If there are ex-girlfriends willing to confirm the rumor... well, maybe Shakrai should be a little more discerning in who he sleeps with or accept the consequences; keeping unpleasant truths private is not the purpose of the legal system.