So I am a parent of underage kids. I have not had to deal with it. I can give you my parental perspective, and also issues I had to deal with at your age.
It is most likely an over-reaction, and if you go back and let things calm down they will come to their senses and support you. People make emotional decisions and then they calm down.
Your parents have the right to make decisions with their money, and as adults themselves they can make moral stands on their crazy ideas.
It might suck for you, but think about how you would feel if someone came to you and told you to pay out money for someone's college. Then they started wasting that money in your eyes.
I am taking your story for truth, so it sucks in this situation.
I got in a physical fight with my drunk dad at 19. I could have stayed, but I left because I figured a grown man shouldn't have to worry about getting in fights with another grown man in his own house. Also, I already tell my kids their college choices depend on how much scholarship money they bring to the table, and their focus and major choices. If most on my dime, their choices are limited to state public schools and possibly local.