It's _badly intentioned_ (and not just UI). Blackmailing you with losing labelling, which worked fine before all that is a clear proof. So "malware" is not really so far off the point.
Feature A exists for years. New feature B enters. If you want to opt out of feature B, you now need to opt out of feature A as well, which you probably liked much more.
I don't know a better term than blackmail to describe this. Thesaurus seems to imply blackmail is for money, but so is extortion, and it doesn't give me good suggestions.
EDIT: Coercion is more correct, but it's way too mild in my perception.
Malicious, not malformed. Malformed would include buggy software, which is not right. Malware intentionally acts against the users will. Buggy software unintentionally acts against the users will.