I don't know the full situation, of course; there may or may not have been other ways to handle it. The Bible says that within our churches "everything should be done in a fitting and orderly way" (1 Corinthians 14:40).
What this pastor did, however, was clearly wrong. Plagiarism -- the technical term for stealing someone else's research or writing -- isn't tolerated in secular circles today, such as universities or the media. Shouldn't Christians have even higher standards? Of course we should. The Bible urges us to "become blameless and pure, children of God without fault in a crooked and depraved generation" (Philippians 2:15).
Perhaps this pastor excused his actions by telling himself he was too busy, or he wanted to give his congregation the best sermons he possibly could, but such choices still involved deceit on his part (and even laziness). The Bible's command is clear: "Do not steal. Do not lie. Do not deceive one another" (Leviticus 19:11). Many pastors use the Internet for research as they prepare sermons (just as they use books and other resources) -- and that's perfectly acceptable, when done with integrity.
Pray for this church as it seeks a new pastor, and pray, too, for your own pastor. Pastors have a serious and often difficult responsibility, and they need our prayerful support and encouragement as they seek to "Be shepherds of the church of God, which he bought with his own blood" (Acts 20:28).