Not quite half - 43.9% in 1933, and that election is not considered by historians to have been anything like free and fair. In the prior two elections, the Nazi share of the vote had decreased from 37.3% to 33.1%, indicating that Nazi popularity was on the decline. If it weren't for undemocratic backroom scheming that handed the chancellorship to Hitler, there might never have been a Third Reich.

So yeah, I think Zuckerberg's statement stands up well even in the face of 20th century history.