To be anti-pain, you would have to be pro morphine from cradle to the grave.
This is exactly where a lot of their ideology falls apart and they intuitively know this is wrong. This anti unwanted pain paradigm is of course not the motivation behind liberal ideology. Op is just incorrect here. Off the top of my head I can think of 3 reasons for liberal reasoning and AUP is not behind any of it. although I could see AUP as being some ad hoc reasoning they apply to it. Here are the main 3 types of liberals I can think of.
1. Slave morality liberals- By far the vast majority of liberals. It's a collectivization of the weak against the strong and they use bullshit ethics that they don't even believe in for a sense of superiority over the strong. They can't actually be physically stronger, wealthier or more socially adept than the strong so they feel better than the strong by attacking ideals like masculinity or by attacking everything as being ableist and even the socially adept are reasoned as having bigger networks because they are using their white supremacy to form them.
2. limousine liberal- The wealthy elite who think of themselves as benevolent dictators who attack the structures of society to reinforce their white savior complex. You can see examples of these white saviors in several hollywood movies that promote this narrative. Either a white teacher who saves a school full of black children by teaching them in a hardcore way, a rich white woman saving a black retarded kid by telling him to tackle people. They are depicting their ideal of a white savior and usually it is in the form of stealing a life story and twisting it to their narrative.
3. midwit- midwit is typically somebody who has an IQ between 115 and 130 and consider themselves smart. They don't realize that if you eliminated the mentally deficient from society and only included non mentally deficient people in average IQ rankings than you will see the midwit is really not intelligent but instead has a mediocre IQ. We also refer to these people as "reasonably intelligent people" When discussing them in an academic setting as to not offend them. Reasonably intelligent children are usually really good at school. They are good at memorizing facts and typically straight A students. Most reasonably intelligent people display . that intelligence by how well they conform to society and often will be praised "This kid really did learn fast that WW2 ended in 1945" Or they really did learn fast how to get along well with peers and to not offend. These people as adults will often "trust the science" and be "debunkers". They aren't really intelligent they just go with whatever the popular narrative is. The popular narrative was that we should all get vaccinated. Now there are some geniuses who agree that we should all get vaccinated, there are also geniuses that disagree. However the difference between the genius who agrees with them is that he has actually done his research and is considering in addition to the science things like the philosophical implications of vaccinating and measuring the trade offs in other areas with requiring vaccinations. The midwit is just following the popular narrative of what he heard on the TV and what all his friends are saying, the ones who are "deboonking" are using statements from the world health organization or other organizations they think of as "official" because they are midwits and they display this by how well they comply to the establishment and established order. The actual intelligent person has questions the midwit does not. If a midwit is told by their parent "Don't say curse words" at 10 years old, they don't do it or they consider it wrong when they do. The intelligent kid asks why and he doesn't settle for answers like "It's just wrong" . they actually give it a lot of thought. Or they ask a ton of questions and are not settled with bullshit answers. They will either decide through good reasoning on their own why cursing is bad or good or neutral but they will not just blindly comply like the midwit. They have actually done studies where they put midwits in classroom settings and ask everyone what 2+2 is and when everyone answers 5, the midwit will change his answer to 5 and also state out loud that his answer is 5. The genius will say 4 and doesn't care about that sort of social pressure. Funny enough the idiot will also say 4 and trust his instincts which makes the idiot and the genius both more honorable than the midwit.
So there we have it 3 types of liberals. 3 moral codes
wokie/normie- Salve morality embodied through liberalism
limousine liberal- narcissist who thinks he is helping the world through his top down elitism
midwit- A conformist who doesn't know better and as soon as the paradigm switches back to the right these people will also be right wingers and funny enough the geniuses might switch back to the left while these midwits just swallow up the bullshit of the establishment that had they been born 30 years earlier they would hate.