Malicious here means "most people who aren't trying to argue semantics or otherwise be smartasses about it would consider it malware". That's why the example I gave is a semi-popular software the allows watching YouTube without ads without a premium subscription, i.e. at least in the case I observed, I don't believe this was weaponized against apps that interfere with their business model.
As for "intrusive advertising is malicious", see the second part of the first sentence.
I'm not being a smartass. Intrusive ads are malware. Adware used to be a category in virus scanners, then stopped when virus scanners wanted to run ads themselves.
Proxying traffic is not malware, since it doesn't affect me in any way.
