Why did yankees killed southerners when they apostated from americanism?

Well that's just the way they are, can't live and let live. It's a lot the same today.

Because they were told by the patriarch-class that losing the control of the resources and finances of the South would be a 'bad thing.'

What they didn't tell the peasants is that it was a 'bad thing' to the resources and finances of the patriarchs retirement and back accounts that were not shared with the dead or their families!"

History is always made by the Rich to keep the Rich rich.

Because 2nd amendment "solutions" are never solutions. A culture that maintains that decisions must be made only by the powerful is a culture that is self destructive since its ruin is assured as soon as it meets an adversary that is stronger.

The slavery was a political issue that the South was losing but they refused to accept that outcome.

Secession was illegal.

Why didn't the South admit to the real reason: slavery. Which is why the Confederate Constitution prohibited any state from abolishing slavery.

I think if the South decided to secede now, a lot of people would be happy to see them go.

There was some killing going on by both sides.