You would still be incorrect... depending on YOUR interpretation of the US Constitution - which may not be valid.
If born in the US to parents who were fraudulently married- and thus had no marriage (it is not a voidable marriage..it is a VOID marriage ) and you are invalidating his status based on Obambi’s British citizenship - you are incorrect. Check British law about illegitimate babies at that time.
If you are invalidating his status based on Obambi’s father’s British citizenship alone..then you may or may not be incorrect. It would be up to a court/Congress to decide what constitutes Natural Born Citizen...and therefore you can’t claim as fact that he isn’t a NBC. ..it would only be a possibility based on legal argument which could be argued both ways.