You all, I think I know why he only goes for mated omegas. They don't react to his pheromones, so whatever they are going on he knows that it's because they want to, not that they are forced to do it because of his pheromones.
NGL, that sounds like it SHOULD be sweet, but that's actually really sleazy. Plus he said he always wanted to steal an omega away, so that makes it worse.
You all, I think I know why he only goes for mated omegas. They don't react to his pheromones, so whatever they are going on he knows that it's because they want to, not that they are forced to do it because of his pheromones.