Does sound like the border official was being overly cautious about the author's role as a journalist.
That said, having traveled around the world on multiple visas (particularly in the US), I can vouch that traveling on any visa other than tourism is a pain in the ass. I'm always ready to be turned away. I usually have a large institution backing my non-tourism travels (a university or a large corporation) and their advice is consistently: don't argue, just turn back then tell our lawyers and let them deal with it.
That said, having traveled around the world on multiple visas (particularly in the US), I can vouch that traveling on any visa other than tourism is a pain in the ass. I'm always ready to be turned away. I usually have a large institution backing my non-tourism travels (a university or a large corporation) and their advice is consistently: don't argue, just turn back then tell our lawyers and let them deal with it.