I think the first point is a logical argument. If two people of different races are both mediocre and they're competing for the same thing, then if as NYCblue has noted, it was a blow to mediocre majorities, it would by extension be a boon to mediocre minorities. And this micro hypothetical, it's a zero sum game.
And I think the second point is something I've described previously. Some people will inevitably judge minorities that benefited from some preference, as not having earned it.
And it's not that crazy an argument. It's basically the white privilege argument in reverse. It's just that some DEI programs are much more explicit then more nebulous things like systemic racism.