I saw the exchange. The headline is a false characterization by a half-educated hack. Trump simply said the present interpretation of the amendment will need to be challenged and may well be found to be wrong. Indeed, several scholarly articles were posted here on the same issue. Trump took an entirely defensible position. The whole bit about repealing the Fourteenth Amendment is just an alarmist straw man.
But A14 does seriously need to be qualified to prevent abuses like abortion on demand, same-sex marriage, anchor babies, etc., etc. It is hopelessly vague. The men who wrote it had no idea what the capacity for abuse by future judges would be.