was the question right and what should have been the right question ?

I think it was a rude question of them, but people should be prepared to answer questions like this. Instead of I can't say, I would have answered something like that it's confidential, that sounds more professional if you don't wanna talk about it. It can cost the job, but at the same time, it may not. It depends on a lot of things... whether they really need a marketing person or what the other interviewees were like... (in my country, pinterviewers can even ask really private and intimate things such as when a woman wants a baby...)