In general, I believe you are correct that most parents who are opposed to the common core also don't understand mathematics, but that's just a symptom of the abysmal way that mathematics is taught[1]. Common core tries to fix this but it falls short because it doesn't actually try to address why children aren't performing well, just gives another way for things to things to go wrong.
[0]: https://medium.com/i-math/why-5-x-3-5-5-5-was-marked-wrong-b...
[1]: https://www.maa.org/external_archive/devlin/LockhartsLament.... (a classic)