Martin R. Gardner says the rhetoric from Church leaders in the 1850's was "excessive," and it later subsided.
Marvin R. Gardner, "Mormonism and Capital Punishment: A Doctrinal Perspective, Past and Present" Dialogue: A Journal of Mormon Thought 12, no. 1 (Spring 1979), 11
While the most fervent sermons on blood atonement were preached during the reformation movement in the 1850s, a period of intense Mormon revivalism bordering on fanaticism, the doctrine also seems to have been defended by nineteenth century church leaders after the excessive rhetoric of the reformation had subsided.