FB has been under intense scrutiny for providing a platform for hate speech, so why should we be surprised that they use automated means to decrease the lead time between posting and removal?
That phrase is hate speech, it just happens to be contained within one of the founding documents of the US. While it is a worthwhile goal for the algorithm to understand the context of it - I don't think we're quite there yet, and I would rather have a few false positives than the avalanche of shit that would exist without it.
As to whether a human removed it, I suspect that from the perspective of the person doing it, it's better to err on the side of caution than lose your job; especially a non-US citizen.