@cheitzig
Since only part of the credit is refundable if you don't have taxable income on the return the non refundable portion has nothing to negate.
Also, if the parents are not able to use the credit due to income limitations then they can forego claiming the child to allow the child to claim the non refundable portion of the AOTC but the child must still indicate they COULD be claimed as a dependent even if the parents will not claim them. Using this option allows at least part of the credit to be used but is wasted if the child has no tax liability.
