Those are a snug slip-fit. Yours may be oxidized and stuck because of that. Might also be the rubber O-ring used as a vibration damper...or a combo. Consider that these are both relatively valuable parts, especially in straight condition. They are also kinda fragile. The trim rings are diecast, a.k.a. "potmetal"...brittle and can be chipped.
You might try applying penetrating oil and giving it a few days to do its work. I'd try using a strap wrench on the ring, itself, using hands only to hold the tube. If that doesn't work, find a scrap of 2x2 that's longer than the HL ear tube, catch the edge of the chrome ring then, carefully holding it in place with your hands, tap the lumber on your bench. It shouldn't take a whole lot to break the bond. The lumber should fracture before enough force can be applied to damage metal and, since wood is comparatively soft, it won't scar metal.