What really seems crucial here is section 6, which begins with this paragraph:
On Mill's account, understanding a social institution consists in observing regularities in the behaviour of its participants and expressing these regularities in the form of generalizations. Now if the position of the sociological investigator (in a broad sense) can be regarded as comparable, in its main logical outlines, with that of the natural scientist, the following must be the case. The concepts and criteria according to which the sociologist judges that, in two situations, the same thing has happened, or the same action performed, must be understood in relation to the rules governing sociological investigation. But here we run against a difficulty; for whereas in the case of the natural scientist we have to deal with only one set of rules, namely those governing the scientist's investigation itself, here what the sociologist is studying, as well as his study of it, is a human activity and is therefore carried on according to rules. And it is these rules, rather than those which govern the sociologist's investigation, which specify what is to count as "doing the same kind of thing" in relation to that activity.The last sentence need not be true. The sociologist can choose to count as the same thing any two things at all. Winch's point is that what actually interests us (presumably and for the most part) is activities as they are understood by those who engage in them. If we want to we can study mere hand-washing, but chances are if we are interested in "understanding human behavior" or "understanding a society" then what we mean is that we want to understand the rules that the people we study are following. And a Muslim who washes before prayer is not following the same rules as a surgeon who washes before getting to work. The criteria for performing the action correctly are (or at least may be) different. In a sense one must already understand what people are doing before one studies their behavior.
Is this a problem? I don't think it has to be. Understanding what something is need not answer all our questions about why it happens. For instance, we might want to know whether hooliganism increases or decreases when unemployment goes up. To answer a question like this we need to know what does and does not count as hooliganism, but then there is nothing to stop our counting instances and comparing them with unemployment rates. The main problem with an inquiry of this kind, I think, would be knowing whether any pattern discerned was a case of causation or mere correlation. Another problem would be knowing exactly what was meant by 'causation' in a case like this. Let's say unemployment tends to increase hooliganism. Still, not all hooligans are unemployed and not all unemployed people are hooligans. And unemployment is unlikely to cause hooliganism in the way that it might (be said to) cause attempts to get a job. A job applicant can explain that he is applying for a job because he is unemployed. A hooligan who sincerely blames his behavior on unemployment is (almost certainly) hypothesizing in a way that the job applicant is not.
I'm not sure what to say about this, but I think that correlations like this could be found and might be quite suggestive. The question that people like Winch and Read might ask is whether finding such patterns really counts as doing science. As long as we see the difference between this kind of case and what physicists do then it probably doesn't matter. But the difference is large. Big enough not only to leave room for doubt about the underlying or true cause, but big enough also for the related but not identical phenomenon of moral disagreement. The moral sciences are not the same as the natural sciences. If atoms or bodies in motion do this or that then there is no room for moral evaluation of their behaving in this way. If violent crime increases when income inequality increases (as I expect it does) this can be appealed to as an excuse or mitigating circumstance, but it does not remove the intelligibility, the possibility, of blaming the criminal. If there is causation here it is not of the same kind as the billiard ball kind. This itself is a fact about how we use the concepts relevant to making moral judgments, a fact about human behavior.
Although here things get complicated and/or confusingly meta. One person might insist that if there is enough evidence of a correlation between inequality and violence then we have no option but to accept that the former causes the latter, and that anyone who denies this is speaking nonsense, is simply unintelligible. Another person might disagree and say that there is room for reasonable people to take various views on the matter. In other words, simply describing uses of language without getting involved in the debate is not simple, and is perhaps not possible in every case. There is not always an undisputed fact about what makes sense and what does not. But often there is. And even when the space of possible meanings is disputed territory, diplomatic negotiations might still be possible. Not necessarily with a view to resolving the moral or political disagreement (although that might be possible too), but simply with a view to reaching agreement about who is saying something, however laughable or repugnant, and who is not. The possibility that attempts at description will get personal and/or evaluative does not rule out the possibility of (impersonal, neutral) description. This goes for both philosophy and social science. But it does mean that in an important sense we are not doing science in the way that physicists are doing science.