1) Mind-reading devices exist in some nations. Determining that someone holds a particular opinion without their having expressed it is technologically possible. Punishing people for opinions determined to exist in their mind through the use of mind-reading devices would be forbidden by this legislation.
2) Inferring someone's unstated opinion requires no great technological acumen, and can be done in even the most primitive nations. Punishing people for inferred opinions would be forbidden by this legislation.
3) Declaring someone to have an opinion and then criminalizing them for it may be possible under some legal codes. This practice would be forbidden by this legislation.
4) Determining that someone is genetically likely to possess an opinion, and using this as an excuse to criminalize the possession of certain genetic or epigenetic forms, is entirely conceivable and indeed could occur at lower technology levels in cruder forms. This practice would be forbidden by this legislation.
There are actual use-cases for this legislation. Therimenjas supports forbidding what this legislation would forbid.
(OOC: Everyone does remember that mind-reading devices are acknowledged in the issue system, right? They're canonical sci-fi components in this setting.)