I can't imagine the Imperials being respectful of the indigenous people they find on Endor but as I said before when the Ewoks first see our heroes their first impulse is to eat them.

Leia was spared because she helped one of their own fight an Imperial which suggests they already don't like the Imperials much.

Threepio was spared because he was gold and spoke their language (he thinks).

There is enough there already to suggest that the Ewoks have no problem eating humans and don't like the Imperials.

Do we (the audience) need more of explanation as to why? We already know that these guys burn Jawas and moisture farmers and it would be hard to get a full run down from a species that don't speak the language.

All that's need is add more explicit evidence that these guys have already taken on the Imperials with some success to establish that they are tougher than they look (to add credibility to the Imperials ultimate defeat).

If the Ewoks are stealthy enough to get passed a Jedi the Imperials may have suffered quite a few losses without having a clue what happened.

The connection with Apocalypse Now should be obvious as Lucas worked on that film and saw the Ewok nee Wookiee Imperial defeat as representing the sort of arse handing the Americans got in Vietnam.

It would also explain where all those traps came from if they were planning on attacking the Imperials anyway.