@Questioner, WRT policy change: I certainly applaud and support your parents convictions and their drive to change the curriculum in your state. You should encourage them to continue to be active to influence and drive change.
WRT to you sitting through this course vs withdrawing. You asked for opinions so here goes - this doesn't sound like it would benefit you personally to withdraw. One thing the Navy teaches in their NSI/ NSO orientations for trainees is to not call negative attention to yourself. This sounds like a risk you can avoid. Don't drop it. Learn to coexist with your strong beliefs and to be able to listen to the beliefs of others. You are not so weak that hearing an opposing view will cause you to melt. You should also point out to your family that you are attempting admission to an extremely competitive SA, where rock star American citizens from around the globe are also with you, vying for a seat. Some of the best young persons in the nation. Ask them not to sabotage your candidacy making you explain something in the interview. When you're in the military and you get an order you don't agree with, will you debate it, retreat/ walk away, or carry it out?
As others posted, will the curriculum change before you graduate? Not a guarantee. Maybe you can make this an application essay that you object and have strong faith but are willing to listen to a view you vehemently oppose, because as a future officer you will/ would do the same. You could use this to show your maturity, conviction of belief, and yet awareness that you'll need to function in the real world.
We can't control who are parents are, and yet you can control in this case whether or not you can just listen to an opposing view. Related to dealing with opposing views? yesterday a co-worker of mine (well, he was a coworker yesterday) from Palestine posted a video of birds attacking the Israeli flag among other rhetoric to our corp. slack channel that was pretty broad reaching in terms of who it included - see pic below. Did I meet with him this morning at the crack of dawn, and carry the mission forward as I do most mornings? Yep- you bet. I have a strong belief of how to treat others, and was offended to the core by his post, but I function/ keep the mission moving forward. Did I also immediately report it to HR yesterday, and by the time 9AM EST rolled around, he is now a FORMER co-worker? Yep - did that too.
Withdrawing because someone is saying something you don't agree with and reporting it as fact? Surely you can and will form your own opinion and can withstand hearing an opposing view, no? If not why oh why would you enter the military? Do some soul searching and see if you can reach a balance here. Soon you'll be an adult but you are making decisions that will impact your future - Good luck.
Officers lead people - including enlisted - if you believe that you will not encounter people with extreme views that you'll need to work with and lead, I believe you are mistaken. Some enlisted are more intelligent, capable, higher performing - the best of the military. Same with some officers, and some from both groups are the diametric opposite of that. You're not the morality police- well you can be if you want to be a clergy, or rabbi, et al. Well, hopefully that's food for thought for you.