Answer:
The statement needed to make the argument valid/strong is:
Premise: Sexual violence is the most vulgar content of all.
Premise: If our movie rating system makes sense, then movies containing more vulgar content will be rated higher.
Conclusion: Our movie rating system doesn't make any sense.
Premise: Violence is, in fact, more vulgar than sexuality.
Conclusion: Violence is more vulgar than sexuality.
By including the additional premise "Violence is more vulgar than sexuality" and adjusting the conclusion accordingly, the argument becomes more valid and strong. It reinforces the idea that movies containing violent content should be rated more highly than those containing sexual content, and it criticizes the movie rating system for not aligning with this understanding.