Linguaphiles

I fed the first paragraph of this news toot in German about a mass demonstration in Hamburg to Google Translate, and something struck me as off. After noting that Google Translate renders the last sentence, Die Kundgebung wurde aus Sicherheitsgründen von den Organisatoren vorzeitig beendet. (a passive-voice construct), as The organizers ended the rally early for security reasons. (definitely active voice), I got curious and went to Bing, which more properly renders it as the passive-voice The rally was ended prematurely by the organizers for security reasons.

So I'm wondering: what's at work here, and how do other machine translators fare on this paragraph?