One argument is that simply criticizing current theories doesn't count as science unless you can also offer a plausible, scientific, competing model. I don't think that's a requirement. Here's an example we can discuss ...
One of the latest posts on Evolution News & Views (sic) is an article by Casey Luskin criticizing the old Urey-Miller experiment by pointing out that their origninal conditions didn't mimic the conditions on the primitive Earth [On the Miller-Urey Experiment, Wikipedia Offers a Citation Bluff]. He goes on to say that scientists still haven't shown convincingly that amino acids (and other molecules) could have formed spontaneously on Earth. Furthermore, the "chirality problem" hasn't been solved.1
Luskin correctly points out that a Wikipedia reference misrepresents the science it reports.
Is this (Luskin's article) scientific? Isn't criticism of current models and hypotheses an example of how science is supposed to work?
1. I agree that the spontaneous formation on Earth of significant amounts of amino acids, carbohydrates, and, especially, nucleotides, is extremely unlikely. That's why I support "Metabolism First." I disagree about the chirality problem—I think we have a good explanation.