The problem is that these things often aren't "obvious". For example, one offense that is listed in the law is §185 of the penal code, which criminalizes insults (I'm not kidding). Because making every insult a criminal offense would make real freedom of speech impossible in practice, actual application of that law is subject to various and sundry constraints as the result of case law of the Constitutional Court. As a result, it's actually virtually impossible to commit such an offense in the political arena (in practice, the law has therefore been reduced to an institutionalized form of contempt of cop for the most part, and occasionally sees use as a modern form of dueling for the few bored and rich enough to pursue a private lawsuit: lawyers at ten paces, so to speak). But to understand that, you do have to be sufficiently familiar with the case law.
That's not much of a problem when an actual prosecutor examines the facts: the case against Boehmermann, for example, was pretty quickly dismissed, because the prosecutor knew it was going nowhere fast. But now let's have Facebook's staff – most of them without legal training – examine the same facts and they may very well get it all wrong. Or, worse: decide to simply not bother with getting it right and just err on the side of caution. The law does not penalize inadvertent censorship, after all.