That's not true. The idea is that love (the romantic kind), leads to attachment, which develops into a sense of propriety and the fear of losing the loved one, which leads to fear and jealousy, which leads to anger. And both fear and anger leads to the Dark Side. Yoda explains it pretty well in Revenge of the Sith. However, the kinds of love that are friendship, charity, compassion are encouraged. Anakin explains that to Padme in Attack of the Clone. Romantic love is not really evil, but it is considered dangerous for a Jedi.
And I'm reminded what Obi Wan said when Luke discovered Leia was his sister:
"Your insight serves you well. Bury your feelings deep down, Luke. They do you credit, but they could be made to serve the Emperor."
What could be those feelings? Could it be love for his sister? I think it's highly plausible. Does Obi Wan chide Luke? No, he says his feelings about his sister do him credit. So this thing about love is not as harsh as you make it.
That's not what passion means here either. Passions are those instinctive emotional drives that exist inside of us. They are the most primal drives that we have like lust, aggression, anger, jealousy, fear. You know, those things that can lead to the Dark Side... The word "passion" comes from Latin "pati": to suffer, to endure. Every religion, spirituality and philosophy advocate some tempering of the passions. The monks that are the Jedi are no different.2> By further extent, all passion is evil. Really love art? Evil. Get super stoked about your writing? Evil. Throwing yourself into helping the poor because you have a personal mission? Evil. According to the Jedi, at least. Passion is evil.
You'd be surprised. Some people like to keep a blind eye, especially about themselves... I see that maxim as a call to not accept "I don't know" as an answer and to always seek knowledge. Especially about the Force. And to remain open-minded.3> "There is no ignorance; there is knowledge" is a stupid maxim, since nobody openly applauds ignorance, really.
When did that ever happen? Because I don't remember any of those "mind purges" in the movies. The only exemples I remember are more akin to mild hypnotic suggestion, quickly forgotten when they are over. Dark Siders will use it for more potent purposes, like the mind probe. It's like telekinesis. A Force-user could use it to take an object, or to crush someone's throat (Force choke).And beyond that, the Jedi Mind Trick is a thing of horror. If it were anybody but "the good guys" using that power, we'd be screaming. It's the only trick the Purple Man in Marvel Comics (Jessica Jones Season 1 villain, if unfamiliar) has. Making people want what you want them to want. Overwriting their memories and desires and free will with a wave of a hand, and it's so easy that Jedi use it for personal convenience. If you want an ability that's "obviously evil", erasing people's free will to control their minds is way higher on that chart than shooting lightning. It's so casually used that those who are resistant to it just chuckle when a Jedi tries to use it on them; they expect the Jedi to do so, it's a fact of life that everyone has been conditioned to accept as normal. They don't even get angry at the attempt.
Sure, the writers largely don't care and use it and because it's the "good guys", it's fine, right? I don't accept that. It's an expression of strength and power over others, for personal convenience. That's Sith motivation.
It's shit like this that are why I want a philosophical reboot in the setting. Jedi and Sith are both deeply flawed, terrifyingly controlling movements. "Oh, but the Jedi let the Republic do whatever, man." Sure, until the Jedi disagree, and then the lightsabers come out. See the trade embargo on Padme's planet, before the Empire even emerges. And worse, they'll purge your minds after and make you thank them for "fixing" you against your original will.