Why have so many people here got a problem with being anonymous on an Internet messageboard?

I don't get it. I really don't. Most people here are anonymous, ie they don't use their real or full name. Every now and then you get a thread by "logged off" or "anonymous" and you get a chorus of people telling the thread starter that he or she's a coward. What's with that? Sure, the poster is also trading under another, different name somewhere on the same board. So fucking what? You post on an internet messageboard, you don't want everyone irl to know you do it, so you invent an internet handle. In a further development, you may not want people who know your internet handle something that you've a mind to post. So you invent another internet handle. I really cannot see how that makes you any more or less "cowardly" than your original decision to use an internet handle. Either the person brings up an interesting point to be discussed, or s/he doesn't. There's no more to it than that.