You are proving your lack of understanding in that the 1% requirement is only required to be calculated in ISA. It does not need to be checked for each flight, that is the MTOW limited aircraft will have the same limit at any temperature/density.
You're proving your lack of understanding by thinking xcel was implying that this is the case.
He was laughing at you, for implying that you had to ensure you meet the minimum 1% climb gradient below 5000 feet.