As others have pointed out, it is a matter of taste what is 'correct' and what isn't. Personally, I favor slightly wide to normal lenses for portraiture, mainly because I get closer to the subject, which makes it a more intimate experience. I'm convinced this changes how the images result, because of the intimacy and the reactions it provokes. I also like the much different perspective and view that results from shorter focal length objectives; again, a matter of taste and a preference for a certain way of working.
But in a situation when I wouldn't want to be close to the subject, for whatever reason, I would compromise and use a longer lens obviously. It could be that the sitter finds it difficult to work with me so close, for example.