The social sciences are part of the scientific discourse. The social sciences are apart of what is traditionally called the soft science. This field is called the soft science as opposed to the hard sciences of physics and chemistry and to a lesser extent biology. This science is considered 'soft' because quantitative data is hard to come by. As the techniques of science advance the social sciences will become less soft and more rigorous.
Yes they should because if you are studying science in general social science definitely would be counted. The Social aspect relates to the psychology of sciences and the mind is the most complicated part of science that is not yet understood just yet. Science is a very vital part of scientific discourse.
While I believe there is definitely a place in this world for social sciences as a way to measure how to do things, I do not believe they need to be scientific discourse because they are not always one hundred percent correct. They should be used to help understand situations though.
Just because the name contains the word "science" does not mean it is actually science. Even computer science isn't really science. Science explains the way the universe behaves, which is why physics and chemistry are real science. Engineers use physics to design things to exist in the universe, not social science.