I know what you are saying and it's difficult to disagree with you. Most people who are pacifists argue that war and killing innocent civilians is never acceptable whatever the provocation and everything can be eventually sorted out by talking..
There is the argument that Hitler could have been stopped earlier, that the British and others knew he was building up an army in the Rhineland even though Germany was not allowed to have an army after the first war. Countries turned a blind eye because they believed he would attack Russia not Europe.
I think the majority Europe is far more aware that waging war in another country is wrong and because the US has never suffered a war on their land, have never experienced the bombing and devastation Europe suffered in the last war, they do not know what it's like to lose thousands of civilians to such attacks, bombing raids etc. and cannot grasp the true horror of war first hand. Because of this they are generally more willing to argue in defence of war and ground troops etc.
The Vietnam war shook America with the huge death toll of their service personnel but that is not the same as endless bombing and destruction of their own homes and the death of their childen in their own country..... imo
58,000 is not a huge death toll. The North Vietnamese used terrorist tactics against South Vietnam. They did some of the same things the Taliban are doing. They killed thousands of teachers and other members of the intelligentsia. They kidnapped people from villages to force them to fight. They killed anyone who opposed them. The US aid was to end this and to some extent it did bu only after we wiped out the Vietcong. The RVN was defeated in 1975 by a conventional invasion by North Vietnam. The Chinese and Soviets poured equipment into North Vietnam, helped them build a massive conventional force and the US in contrast abided by the 1973 peace terms. We stopped giving them military aid, fuel etc. They launched a limited invasion to see if the US would respond. We failed to use out air power to route them like we could have done and we failed to provide fuel, weapons etc. The test was for a simple reason they didn't want to lose their entire military to us. Our inaction convinced North Vietnam we would not respond to a large scale invasion. They launched it and they took over South Vietnam. The only thing the US did was fly out those that we could and took in any refugees who could manage to escape on their own. They took over and brutalized the population of South Vietnam, took their wealth and freedom. Undoubtedly they would have been bette roff under RVN rule but no one would take a stand to help them. The only reason the DRV had the power to take over was because China and the Soviets supplied them with so many weapons or they never would have been able to do it. Today Vietnam has a mixed economy but that doesn't help those they robbed, killed, or brutalized and they still have a tolitarian government today not a democracy.
When one side is using force the only way to counter it is with force of your own. If we didn't stand up in Korea then the people of South Korea would be just as miserable as those in North Korea. The same troublemakers who armed North Vietnam armed North Korea and blessed their invasion. Because we aided South Korea those in South Korea live in a very prosperous country with a strong democratic government.
The difference between what happened in Korea and Vietnam is that in 1950 we refused to allow the North to take over while in 1975 we allowed North Vietnam to invade with impunity. The ones who suffered from that decision were those living in South Vietnam.
People can make up any garbage they want at its core what it amounted to was the leaders of the US government didn't feel like spending more of our blood and treasure for the benefit of the people living in South Vietnam.
Just like the Allies stabbed the Poles in the back and refused force the USSR to allow the Free Poles to take over in Poland after WWII. The Free Poles even fought to liberate France and in exchange they got sold out. The USSR was allowed to steal land from Poland that they took over in 1941 when they carved up Poland with Germany and started the whole mess and the Allies allowed it.
When the country being subjugated is some country other than yours it is easy to say who cares about them- let them live under a horrible regime with no freedoms too bad for them.
That's really what it amount to- people saying too bad for the Syrians and Iraqis coming under ISIS rule and too bad for the Syrians being brutalized by Assad. We the World who pledged to stop human rights violations will do nothing because we don't want to spend the effort involved.
We will stand by as Russia helps Assad stay in power by brutalizing and killing those who want democracy and will stand by as Isis kills people and to make it see like we do have a heart what we will do is take in refugees if they can manage to survive to make it to the West- that is how we will be charitable.
Evil wins when good men do nothing. Putin and other bad men are doing things but the good men are doing token things that amount to nothing.