The problem that they don't want is using an extension cord without a ground line. The amp draw is negligible, and the cord don't even have to be that heavy. I've used cords outside & in the shop with mine.
'97 VN1500 91 Cubes Of Custom CLASSIC
Vance & Hine 2to1
engine, forks, ignition & carb mod's
WebCam cam & rockers hard weld & grind
NEW TOP END, NO LOOKS ALL GO GO
Maxx intake manifold system & super G carb 44mm