Okay, so we don't get inside any of the antagonists' heads, but that's not the best way to determine if a character is an antagonist. For that, we have to check what they're doing. Are they trying to beat down the nonconformist in their midst? Yes?
Congratulations! We have an antagonist.
Some of them, like the racist Samuel Teece (from "Way in the Middle of the Air") and drunk wife-beater Biggs, are awful. We hate them, they hate the protagonist, it's a match made in Heaven.
But not all of the antagonists are so bad. Father Stone isn't a bad person; he's just gung-ho about his cause. But the minute he tells Father Peregrine to get serious (i.e., stop being different), you know he's an antagonist. Or Yll, who tells his wife to stop dreaming and work harder (try this with your wife—she'll love it).