At a Mass at which I assisted this past weekend, the homily was 100% hard-core right-wing politics. The readings were barely mentioned. (A friend leaned over to me and said, "Is this a Ron Paul campaign commercial I just wandered into?".)
I was not impressed or pleased, despite the fact that I agreed with maybe 90% of what the priest said. Political opinions, other than those on matters essential to the faith like abortion or homosexual "marriage" on which faithful Catholics are not free to disagree, don't belong in the pulpit! That includes "right-wing" opinions as much as "left-wing" ones.
And so, while the bishops are certainly free to express their views on any topic, neither we nor they should be "putting those opinions in the pulpit" by confusing them with the essentials of the faith.
AMEN! The priest misses an excellent 'teachable moment' when he ignores the Scripture readings in his homily.