Douglas S. answered 6d
10+ Years Experience Teaching History, Philosophy, and Writing (PhD)
I'm surprised this question has remained unanswered since 2019! As a film buff and former Ethics prof, I'm appy to help :)
The key ethical themes in the Purge: Election Year are utilitarianism, deontology, and integrity. (One could try to work virtue ethics or metaethics into here but they're not as highlighted in my opinion in the film.) The government instituting the purge is operating on Utilitarian principles. Here, the "ends justify the means" and it doesn't matter if some people die if it leads to greater long term happiness. Assuming for a moment that the government is right about the fact that legalizing crime for a day would lead to long term happiness, this conflicts with deontological ethics, which focus on the rights and autonomy of individuals to decide what happens to them and their bodies and act on accurate information without being deceived or lied to.
Obviously, the government is lying to the people about people's willingness to partake in the Purge day and the success of the program (as seen in one of the other movies), so even if their Utilitarian calculus (= most pleasure and least pain for greatest number of people) were correct, there is still a major Deontological rights violation to consider.
But the fact that the government knows their program isn't actually successful but does it anyway to stay in power and not be shamed into admitting they are wrong becomes a question of integrity and authenticity. These were key themes Bertrand Williams used to critique Utilitarianism, and "bad faith" or acting against inauthentically was famously explored by the French Existentialist Jean-Paul Sartre.