Uh, we don't. What liberal ever said they love North Korea?
I just don't want war with North Korea, especially when North Koreans themselves are open to peace talks.
North Korea is a brutal regime, but the fact is, we're the aggressors here. North Korea and South Korea were originally just "Korea", and then Japan invaded Korea and annexed land off of the southern tip of Korea and turned it into a Japanese colony. Korea then went to war to take their land back, but by that time the US inherited the Japanese colony because they just defeated Japan during World War 2, so the US ended up being caught up in a war and killed 1/5th of the entire Korean population.
A few years before the Korean war started, the US established a new government in the annexed land called the Republic of Korea (ROK). In the US we call this "South Korea". But neither Koreas call themselves "North" or "South" Korea, but simply "Korea". North Korea calls themselves the Democratic People's Republic of Korea (DPRK).
After ROK formed, the UN immediately declared that ROK was the only valid government and refused to recognize the DPRK, despite the fact that the DPRK was there first and it was their land. The international community made no attempt at peace between the DPRK and ROK and simply wanted the DPRK to be destroyed.
Ever since then, the DPRK has been afraid that they will be invaded again, and they've pretty much turned their entire country into a military state. They don't invest any of their money into the people or the economy, but instead into building up their military. The only thing the DPRK even has is a military, they don't even have food or electricity, but they have tanks and nukes.
Yes, every sane person recognizes that ROK is a million times better than the DPRK. ROK is a great place to live while the DPRK is one of the most oppressive regimes on the planet.
But they're not going to improve by constantly being aggressive with them. Their country won't be brought into the first-world when they are constantly afraid that they will be invaded again and wiped off the face of the map.
If we went to war with North Korea, it would be a horrible disaster for South Korea as they would receive the brunt of all the attacks. South Koreans don't want this, either, as they elected Moon Jae-in specifically because he was a peace candidate.
Why do so many warhawks and neocons in the US think they should have the right to start a war with North Korea when it will be South Korea who will face the brunt of it? North Korea is open to peace talks, so why insist on trying to destroy North Korea?
People think that just because we don't like a country, we should attack it, even if they aren't attacking anyone and want peace.