The main utility of suppressing ideas is suppressing the ability to coordinate around them. If a lot of people hold some latent antisemitic ideas, but anybody expressing explicit antisemitism is regarded as a sort of loathesome toad, that prevents the emergence of active antisemitic politics, even if it’s a wash in terms of changing any minds (suppose, plausibly, that conservation of expected evidence means that “why can’t you say this” more or less balances out people being exposed to fewer arguments).
Obviously there are plenty of costs as well—enforcement mechanisms can be weaponized for other purposes, preference falsification also makes it more difficult to identify the good guys, etc. Your original contrarian take is still a largely defensible one, though really I think the nature of the internet is such that it’s kind of a fait accompli under current conditions that it’s harder to make things taboo and prevent the coordination of your opponents.
If you live in a universe with self-consistent time loops, amor fati is bad and exactly the wrong approach. All the fiction around this, of course, is about the foolishness of trying to avoid one’s fate; if you get a true prophecy that you will kill your father and marry your mother, then all your attempts to avoid it will be what brings it about, and indeed in such a universe that is exactly what would happen. However, a disposition to accept whatever fate decrees for you makes many more self-consistent time loops possible. If on the contrary your stance is “if I get a prophecy that something horrible happens I will do everything in my power to avert it,” then fewer bad loops would hypothetically complete, and you’re less likely to get the bad prophecy (even though, if you do, you’d be just as screwed, and presumably less miserable about it and foolish-looking than if you had just accepted it from the beginning.)
(If you live in a nice normal universe with forward causality this advice may not be very useful, except in the sense that you should also not submit to prophecies, albeit for different reasons.)