This sentence is telling the reader that a movie DID saturate most of it's scenes in Coke and Nike (meaning that they had Nike and Coke products appear in most all their scenes). 'Would' isn't implying an assumption, because they are saying that the movie executives did do that. In this context 'would' is the past tense of 'will.'

it is emphasizing that there was a choice being made and there was in this case a better alternative. The person writing the text thinks whoever made the movie made a bad choice and is questioning why they did it.

In this case "would" means that they "did". To use another example- Suppose your friend spilled coke all over your new shoes and you exclaim- "How could you do that?" In your second example- we can assume that the action has not been done but if it would.... The difference is here- In the first sentence notice: "it upsets us..." so, it has already been done because it upsets us. In the second sentence (your example): "it would upset us..." so, it hasn't been done but if it was... -Eric

Your alternative is not quite the same. The original sentence implied that the thing actually happened and the writer is upset with it. Your alternative is saying IF it were to happen you'd be upset.