-some guy- is a tool. Any layers of fabric will be better than nothing at inhibiting a virus from getting to your airway, even if the fabric is only catching .0001% of particulates. Where it becomes iffy (worse than nothing) is when that fabric is a) not being sterilized often enough or b) if one side of said fabric (like the vinyl side) is holding a large viral/bacterial load from the external environment, and is then put over ones airway or c) said fabric is infused with bacteria/fungus/viruses from the wearers own moist exhalations/sweaty skin. See point a. Most infectious bugs prefer warm, moist environments so air your neckwear out often, wash it frequently and in a pinch, spray it with Lysol.

Reality is, nobody is seriously wearing a gaiter for viral protection, there are medical grade masks for that. Feel free to continue recommending gaiters as a deterrent to frostbite, and suggest washing them often.