I can see a parent grounding people from cubes (when I was younger, my parents confiscated all my cubes for two weeks because my grades fell.), but I could never see a parent throwing away cubes. I'm pretty sure your parents took a last-minute stand to "force you to quit", not necessarily ground you.
As I understand from your relatively cryptic post above, you said "yes" to a question without thinking? If so, your parents may think you told a huge lie, or went outside of their morals (very common with religious parents, if you are in a religious household this may explain it) and decided to throw them away in a rage. I would take a few days to cool off and talk to your parents about it in a few days, and try to meet the common ground, and apologize. I'd avoid talking about buying new cubes for a while, as they would probably be super unhappy. As well, I'd try to contribute more around the house. Get off the phone and clean your room and the house, try cooking dinner or doing the family laundry. This will get you on the good side of your parents.
Overall, This may be a good time to back away from cubing for a bit and participate more in life. Even though losing your favorite hobby for a bit sucks, a break can be a really good thing.
