The Cuban missile crisis was over nuclear missiles, not conventional. NATO put nukes in Turkey and Italy, Russia tried to match with Cuba. The crises ended when both sides agreed to withdraw nuclear missiles from said countries.
If my irrational neighbor says my quiet, well-behaved dog is actually barking all day and night, growling at him as he walks by (even when the dog is inside), and if I don't stop it he'll break into my house and kill my dog: I keep my dog inside, put up some cameras, clean my gun and file a police report.
Yeah, Ukraine is downright angelic compared to Putin's Russia. They actually had the potential to become a thriving democracy and regional economic power, something Putin can't have on his border. Makes him look bad and destabilizes his legitimacy, same reason the Soviets put up the Berlin wall.
If my irrational neighbor says my quiet, well-behaved dog is actually barking all day and night, growling at him as he walks by (even when the dog is inside), and if I don't stop it he'll break into my house and kill my dog: I keep my dog inside, put up some cameras, clean my gun and file a police report.