Be specific as to which ones you are referring to along with proof to back that up. There's nothing stopping them from releasing secular albums. And while I will admit that the quality of CC music in the last 5 years has deteriorated (the quality of pop music in the last 15 years has deteriorated much more), if they can make a living with a CC label, they can make as good or better a living with a secular label.
He probably could, but it's probably best not to do so. It is good to be "discerning" about what we listen to, and to evaluate individual performers, but it can get a bit scary to identify individuals as "willing to sell their soul to the devil."
Now, if you want to identify particular performer's *songs*, or things they've said, or ways they've behaved, that's another thing. If you want to critique the different ways that Sandi Patty and Amy Grant have behaved in light of their marital unfaithfulness, vs. the way that Michael English did, that seems all right to me. If you want to critique the heretica song "Above All" that Michael W. Smith sings, that's probably fine.
But it's dangerous to say that someone's "selling their soul to the devil"....