We are not told the prescriptivists’ view of the descriptivists’ motivation or whether any part of that motivation relates to some kind of dislike or hatred of prescriptivism.

We have no support for the idea that the prescriptivists think they stick to the scientific method more than the descriptivists do. Nowhere in the passage do we get any indication of the prescriptivists’ belief about their own adherence to the scientific method or a comparison to the descriptivists’ level of adherence.

Supported. The prescriptivists believe that correct usage helps to include people in communication. This is arguably more egalitarian than what the descriptivists want. If we don’t try to correct people’s usage, maybe the people who use language incorrectly will end up excluded from free exchange of ideas with the people who do use language correctly.

The passage never suggests prescriptivists think descriptivists are unaware regarding anything related to the origins (etymologies) of words. Maybe the descriptivists know all the origins, maybe they don’t – we don’t get the prescriptivists’ view about this.

The passage never suggests that prescriptivists think that descriptivists’ empirical observations “generally” support prescriptivist views. Although the passage does discuss some empirical observations about language change in the last paragraph, that doesn’t support a claim about what is “generally” true about empirical observations or whether those observations were the descriptivists’ own observations.