It's not propaganda - it's one thing taking pictures of waving and (out of context) gestures of people (who are equally unpopular in their own right) but Elon's 'salute' was a full-blown mimicking action and this is off the back of political and societal stances he houses, so whether there was any malice or if it was just an awkward moment from a immature 53 year old, it doesn't really set a good example. This happening off the back of him getting into petty squabbles with gamers and then trying to ruin their livelihoods because they outed him and a dishonest person.
If I go into a room of important people and shove my middle finger in all their faces, I can't turn around and say it was a harmless misunderstanding, unintentional and I didn't know how it would reflect.