Which doctrine are you referring to? The Catechism of the Catholic Church addresses the issue of abortion insofar as those who procure one: 2272. "Formal cooperation in an abortion constitutes a grave offense. The Church attaches the canonical penalty of excommunication to this crime against human life. 'A person who procures a completed abortion incurs excommunication latae sententiae,' [CIC, can. 1398.] 'by the very commission of the offense,' [CIC, can. 1314.] and subject to the conditions provided by Canon Law. [Cf. CIC, cann. 1323-1324.] The Church does not thereby intend to restrict the scope of mercy. Rather, she makes clear the gravity of the crime committed, the irreparable harm done to the innocent who is put to death, as well as to the parents and the whole of society."
As for the church and its hierarchy, the Catholic Church is Christ's bride (Ephesians 5:29) and has "no spot, wrinkle or blemish" (Ephesians 5:27). Individual clergy may commit sins, even popes commit sins because in the Church there are both "weeds and wheat" (Matthew 13:30).
Communion should be denied to politicians (and others) who call themselves Catholics but publically protect abortion.
Don’t understand why this is such a difficult concept.