And by doing so broke the rules. Regardless of whether he could see the cause or not, that zone was yellow, and his dash, the yellow flags and his radio will have told him so. The marshals in proximity may have been intended to return to the track to collect debris, hence the zone remaining yellow. Had Hamilton spun whilst using his DRS, and hit a marshal because he couldn't be bothered to slow down a bit, then he'd look even stupider than he already does. Being a good racing driver he won't be on the limit in FP1 of a brand new, dusty circuit whilst testing things for the race, but that in itself doesn't rule out mistakes. Indeed, he went quite a lot quicker later in the session, suggesting that this lap wasn't on the limit (as would be prudent).
MY argument and THE argument are one and the same.