I am reading a speech delivered by Sara T. Smith at the Second Anti-Slavery Convention of American Women.
I am confused what exactly the boldfaced lines in the paragraph below means. The context here is that Smith is encouraging women to participate in the abolitionist movement.
By the Constitution of the United States, the whole physical power of the North is pledged for the suppression of domestic insurrections, and should the slaves, maddened by oppression, endeavor to shake off the yoke of the taskmaster, the men of the North are bound to make common cause with the tyrant, and put down, at the point of the bayonet, every effort on the part of the slave, for the attainment of his freedom.
What does it mean for the men of the North to make common cause with the tyrant? Teaming up with a tyrant to put down every effort on the part of the slave sounds quite evil.
I believe I am missing the point here.