Those of us who see the US as an aggressive military empire are baffled by the complete silence of the mainstream "left" in the recent war crimes of Obama and his Secretary of State Hillary Clinton, such as the destruction of Libya, or Obama's drone wars and assassination program. When Bush announced the invasion of Iraq, thousands of people marched in the streets. But when Obama bombed seven mostly Muslim countries (Afghanistan, Iraq, Libya, Syria, Somalia, Pakistan, Yemen) nary a peep was heard from the "left". When Trump issued a travel ban on the same countries bombed by Obama, the liberals were outraged and marching in the streets again. What is going on? Isn't bombing worse than a travel ban? It doesn't make any sense, does it? Shouldn't it be explained?
The main issue taken up by American liberals in recent years was "identity politics"; rights of oppressed groups such as gays, transsexuals, women, etc. This is absolutely the right thing to do. Transexual women are apparently subject to the highest murder rate in society. Consider the case of Alan Turing, a homosexual who solved the Nazi communication code in WWII, and basically invented computers. He was hounded into jail by Christian moralists, given chemical castration, and committed suicide in jail, all because he was gay, a great thank you for helping defeat the Nazis (see the film "Imitation Game").
Aside from the rectitude of supporting these oppressed groups, what drives this vehement effort by the left? The key is that it doesn't threaten the economic, political, or military establishment at all. If anything, it gives corporations more consumers, the military more cannon fodder, and the Democratic Party more voters. It is completely safe, but safe from what?
A key to understanding the phenomenon of capitulation to Democratic war criminals while opposing Republican war criminals comes from my 92-year-old dad. He supported Johnson's Vietnam war policy, and voted for Nixon instead of McGovern in 1972, despite being a lifelong Democrat. He explained that the Republicans always called the Democrats "soft on defense" and "soft on communism". Throughout the cold war, Democrats always had to prove their toughness on "defense", particularly after the McCarthyite witch hunt of the 1950s. Many liberals allied to the communist party, or even just accused, lost their jobs, livelihood, social standing, or were even jailed. The intimidation worked (see the film "Trumbo"). Democrats became big supporters of the military. The only time they actually opposed it was when their children were getting drafted during the lottery for Vietnam. As long as volunteers and mercenaries are fighting, it really doesn't affect them much. Foreign policy is far away and they can ignore it.
Fast forward to 9/11, and remember the famous Hermann Goering quote, "All you have to do is tell them they are being attacked and denounce the pacifists for lack of patriotism and exposing the country to danger. It works the same way in any country."
9/11 was a major trauma to everyone in the US. People who are traumatized do not think logically. They are easily manipulated. Bush immediately said, "You are with us or you are with the terrorists". Most people, including most liberals, believed that Islamic terrorists attacked the US on that day. It doesn't matter what actually happened. That is what people believed, and the Goering philosophy was immediately brought to bear on it: If you don't support the government, you are a traitor. Who wants to be a traitor? I think this partly explains the blind support for Obama's bombing of 7 Muslim countries by leftists.
Consider the CIA's MKultra program and the psychologists who were involved in the CIA torture program. If nothing else, it demonstrates that the CIA "Deep State" takes psychological operations (Psy-ops) very seriously. They have an army of psychologists advising them on the best way to manipulate the population. Is it any surprise that if the best minds are working for them that they are successful in manipulating the masses? Remember in the "Shock Doctrine" that trauma is used as an opportunity to reprogram people and society. I think that 9/11 served this function for Democrats in America.