Famous people leach fame into others by interacting with them. The easiest way to force someone to interact with you is to hit them somewhere vulnerable. Mr Schilling either wasn't aware of his vulnerability or hoped that it wouldn't be exploited. When it did get exploited, he didn't try to hide it, leaving a gaping wound for even more famewhores to leech fame from him. It worked, because I saw their tweets and I'm not even a baseball fan.
Compare that with someone sufficiently invulnerable, Obama for instance. Or even Chuck Norris.
The other fact is that with a large audience, it'd be silly not to expect that some percentage would be murderers/rapists/other unsavoury types. Getting a dozen offensive tweets out of a million-strong audience is still only 0.000012%, orders of magnitude less than the actual threat of rape.
Compare that with someone sufficiently invulnerable, Obama for instance. Or even Chuck Norris.
The other fact is that with a large audience, it'd be silly not to expect that some percentage would be murderers/rapists/other unsavoury types. Getting a dozen offensive tweets out of a million-strong audience is still only 0.000012%, orders of magnitude less than the actual threat of rape.