Q. 1. Why is it that we never hear of Bishops excommunicating the politicans who support abortion?
A. 1. According to the Catechism of the Catholic Church,
"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." (C.C.C. # 2272)
That means that anyone, including politicians, who publicly support abortions, are excommunicated "latae sententiae." Those two Latin words means that they are automatically excommunicated. There is no need to inform the politicians of their excommunication. While it is desirable that when a politician publicly supports abortion, the Bishop of his diocese should make a public proclamation of excommunication, most Bishops prefer not to do so. Accordingly, they shall be answerable to God for giving the impression that it is alright to support abortions by their silence.
One may ask, "Why will the Bishops answer to God if the politicians are already excommunicated anyway?" It is because these politicians, having been excommunicated "latae sententiae," continue to receive the Sacrament of Communion at the hands of the Bishops while they are not in a state of grace. These Bishops refuse to publicly deny them the Eucharist. By their actions, they are saying that it is alright to receive Holy Communion in a state of mortal sin.
Yet, the Holy Bible states, "For whenever you eat this bread and drink this cup, you proclaim the Lord's death until he comes. Therefore, whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of sinning against the body and blood of the Lord. A man ought to examine himself before he eats of the bread and drinks of the cup. For anyone who eats and drinks without recognizing the body of the Lord eats and drinks judgment on himself." [1 Cor. 11:26-9]