Yes, I'd have signed up with the Union to help wipe out the traitorous slaveholders and help free the slaves. (Normal)
I thought the US was imperialist and evil?
Again, Marxists have a different understanding of Imperialism than do non-Marxists. Whereas you guys refer to imperialism as a government policy, Marxists understand imperialism as the end result of monopoly capitalism, in effect, the highest stage of capitalist development heretofore developed. See V.I. Lenin,
Imperialism: The Highest Stage of Capitalism for the most robust case for this argument, and Nikolai Bukharin's
Imperialism and World Economy if you're interested in getting at the Marxist understanding of imperialism.
Imperialism in Marxism refers to non-competitive, monopoly capitalism. The United States was not a fully capitalist society in 1860 because half of it still engaged in slave-based production. Supporting the Union means wiping out slavery and allowing the full development of capitalism, which is the position that Marx and Engels took and the position that socialists at the time held up as the correct one, and rightfully so.
And get off this crap of implying I'm anti-American. Opposing the foreign policy of the United States in the here and now does not imply that I reject the country of my birth or the things that I has gotten right over the years. You'd do well to avoid such accusations, given that you're one step away from advocating America hitch itself to whatever Israel wants to do in the Middle East as it is. That's far more 'anti-American' that criticizing the post-Civil War foreign policy of the United States ever could be.