I agree with you. You can and should point out shortcomings of work done by others in a respectful way. Even turn it around, if possible, as your example shows.

I agree with you. You can and should point out shortcomings of work done by others in a respectful way. Even turn it around, if possible, as your example shows. Sometimes, however, there is no easy way to avoid saying what is missing. As an example, consider the case when the published research, without giving any explicit justification, does not address one aspect of a problem that the other researcher working in the same area finds important. But even in that case, you should not fail to acknowledge the work that you are building on. As another comment suggests my interpretation of 'negative citation' is probably less strict. I considered negative even the case of pointing out a shortcoming in a polite way, without questioning the validity of the work in a confrontative manner.