Now that's downright funny but to be expected. Nothing against the author of that letter but there were others in the Union Army who were not so picky on taking things.
It really comes down to what one wants to believe. I could believe my 2xGGrandfather and his brothers all joined the Confederate Army to be together in a common cause but they all ended up in different units. Theory 1 blown. Now, I just think they did because it was the thing to do. I honestly do not believe this line had any idea why they were fighting. Now, others, from Georgia and Alabama, they had a bit clearer picture. That still doesn't mean I know why they did what they did. I have no written record, letter, note, nothing, that tells me why they joined the Confederate Army. One thing I do not believe is that any of them went to war to preserve slavery. They didn't have any.
I don't think we in today's terms can conjure up a real one size fits all reason. But back then, in 1860, they had Grandfather's who were part of the beginning of this nation. I can see how they may have been thinking if it worked once, maybe it would work twice. They were dead wrong.