The cult-like behavior comes from their sheer commitment to the greater good. The Order is socially engineered so all of its members always prioritize the greater good. They train Jedi from birth so they never meet their family and prioritize them over the greater good of the galaxy. They don’t allow Jedi to fall in love or even have friends because the galaxy’s history books are full of Jedi who turned to the dark side for their friends. It’s dehumanizing, but the Jedi justify it because the Force gives you an immense amount of power, and if you can’t give up your own humanity for the greater good, you don’t deserve that power. Anakin, the one who wasn’t brainwashed from birth, who will fall in love and have a child, is going to be the one who ultimately destroys the Jedi Order and hands the galaxy over to Palpatine.

The Jedi are still flawed though, and if I were to actually write this I’d like to frame it to make the argument that the greater good itself is not for the greater good. The Jedi and the Republic tolerate slavery because the effort to end it would cost many times more lives than it would liberate, and (temporarily) tolerating some evils is for the greater good. But you can’t exactly tell a slave that their slavery is a good thing, and if it turned out that the Chosen One is a former slave, you’re going to make a natural enemy of him by continuing to tolerate slavery, even if he recognizes ending slavery would let out more evils than it would abolish.

That’s the way I interpret the actual Prequels as well, even if it’s not what George Lucas thinks, and blah blah blah.