Yeah, this topic was pretty much guaranteed to go to hell.
Many all-seasons are barely better than summer tires in bad conditions. Some all-seasons are passable to pretty good, but many are just horrible crap even in slight slush. In that sense it's hard to argue the point.
I've driven on summer tires in the snow with AWD (not intentionally, but because of unexpected snow in Texas.) It "works" in the sense that you generally are safe from getting stuck in the light stuff, but you have to account for LOOOOOONG stopping distances and have to take turns at an absolute crawl. Even in light snow it's pretty terrible.