Well 60,000,000 people did then die, so it seems a reasonable level of preachiness.
A very honourable mention to Alexander Korda.
Particularly 'Things To Come', his 1936 film warning of the rise of fascism in Europe, global war and the dangers of air bombardment (thereby bringing mechanised warfare to civilian populations for the first time).
https://en.wikipedia.org/wiki/Things_to_Come
And yes, it is based on the HG Wells story.