In other words, they were lazy drunks

Salon:

Better than any history I’ve seen, Goldfield tracks the disturbing links between abolitionism and nativism. In fact, he starts his book with the torching of the Ursuline convent in Charlestown, Mass., in 1834, a violent attack on Catholics which Goldfield shows was “incited” by Lyman Beecher, the father of the Beecher clan, most of whom turned out to be as anti-Irish Catholic as they were anti-slavery.

To evangelical Protestant nativists, Catholicism was incompatible with democracy, because its adherents allegedly gave their loyalty to the Pope, not the president, and the religion’s emphasis on obeying a hierarchy made them unfit for self-government.

Also, rebellious Irish Catholics didn’t show the proper discipline or deference to conform to emerging industrial America.