Think of it like this:
"If possible, so far as it depends on you, live peaceably with all."~Romans 12:18 ESV
To live peaceably with others, you don't need to agree with them. You can offer as much respect as possible without agreeing with your parents.
I can't say I know what your situation is like, though I understand on some much smaller scale. I left my childhood church going on two years back, and it caused a lot of tension between me and my mom. The changes included me leaving behind a specific teaching that she considered of utmost importance, and she didn't like that. She lashed out at me very strongly a time or two, and the rest of the time kept saying how she felt like she failed to raise me properly and how she didn't want me to corrupt my younger brother. Looking back, I think she was just very concerned and scared for me and didn't know what to make of my sudden shift in views. (It wasn't sudden, but I had kept it hidden from her for a long time knowing it'd upset her.)
She wasn't part of a cult, though. Just a sub-denomination with a few very strong opinions.
I have enough of an idea to know that your situation is not fun, and a tough one.