In this poem, the words pure and religious are used ironically. They actually mean impure and irreligious. Obviously, the poet think of alphas as a dunked who does not observe religious teachings.
Needless to say verbal irony is difficult, and sometime a dangerous device. In oral discourse, the ironical intention may be conveyed by the tone of voice, gestures, and facial expressions. The poet, on the other hand, must depend upon the reader to be alert to the verbal counterparts of voice,gestue,and expression. He invites the reader to read between the lines.