“They would taste the vacuum of space long before they reached the destination.”
Great, then you get a decade or two of peace before the next generation grows up, and then what are you going to do? Execute half of them if they start espousing the wrong ideas?
You need to think of our the determination, fortitude and purpose of our early explorers, pioneers and settlers. It will take many generations before leisure time might allow brainless self-centered fools to think of their own causes and amusements. It will not be like Star Trek or Star Wars. The sluggardly will find themselves on the wrong side of an airlock. As I said, air is expensive when you have to make your own. It will not be wasted.