Heresy St. Thomas (II-II:11:1) defines heresy: "a species of infidelity in men who, having professed the faith of Christ, corrupt its dogmas... There are, therefore, two ways of deviating from Christianity: the one by refusing to believe in Christ Himself, which is the way of infidelity, common to Pagans and Jews; the other by restricting belief to certain points of Christ's doctrine selected and fashioned at pleasure, which is the way of heretics."
This is Archbishop Chaput we're talking about here. He's kept a recently convicted sex offender priest on the Archdiocese payroll. Why should he excommunicate a Catholic politician?
I agree. The One Holy Catholic and Apostolic Church routinely denies participation in the Eucharist to other heretics such as protestants, mormons and other assorted Truth deniers, why is it so hard to deny heretics within our midst?