Isn’t it fairly likely that by the time we figure out how to build something to send people to other habitable planets, we’ve also figured out how to stop people aging. Or cryogenics. Or a robot that can grow humans when it gets there.
I think y’all are putting way too much emphasis on liberalism. And I say that as a born-and-bred hippie, so don’t get the idea that I think it’s bad - I’d go off my rocker if I had to live in a tin can and obey the captain and all that. But if the last 8000 years have proved anything, it’s that people can get used to all sorts of shit, and deal with it. I think a smallish tribe would be the best analogue for this - everyone relies on each other to live, your options are obey the chief or get chucked out to fend for yourself (admittedly, solo hunter-gathering is still a step up from a one-way trip out the airlock, but it’s still no path to greatness). In fact, I think you’d have to adopt a lot of the same attitudes - the captain is right, no matter what, some of your kids are going to be problematic, and you’ll probably have to beat obedience into them - it won’t be pleasant, but humans are bastards enough to get the job done. Rum, sodomy, and the lash, right? Hell, look at old whaling ships - multiple-year missions, little-to-no outside contact. Give people enough work to do, a carrot (rum) and a stick (the lash! Get your mind out of the gutter!). Also, know that any ship you send is a risk, and send a few as backups.
Lots of ideological differences get settled with reasonable debate, too - creationism vs evolution didn’t lead to mass slaughter in Victorian England, did it?
Hence my “don’t put all your eggs in one basket” idea for a fleet rather than one ship. But in the case we’re discussing, the lie only comes out after the destination is reached. If it leads to bloody war then, well, at least the colonists won’t be *in *that tin can, so not as vulnerable.
It seems people are envisioning a ship with several thousands of people on board. Which means that you wouldn’t be in a situation very different from most people during most of history. Not much opportunity to leave your village/town, and you have to find your place in this small society. Can’t get the girl you wanted? Pick another, even though the pool is limited. Your job sucks? Find another job on the short list of existing jobs. Basically, you’d do what people have done for millennia without going on a killing rampage.