Which is a tough dilemma when you work on something for the love of it. Your work on code for it to be used, but if someone bullies you with something like : change your license or get lost, well, it's a tough decision.
Now, in this case, CUPS on Apple product is not the only use of CUPS, but being able to claim your software runs in Apple product is certainly a nice to have.
If I own something and I want to control the term of how it's used, that's not bullying. Isn't that exactly what licensing is all about in the first place? If that's 'bullying' then every OSS project with a license is also bullying...
