Economics can attract people making wild claims because it is difficult to truly prove or disprove some claims in the subject. Still, there is good science done in economics, though conducting science is more difficult in fields like economics than others. I think it is important to distinguish between microeconomics and macroeconomics here. It is possible to conduct controlled experiments in microeconomics, but in general it is difficult and often impossible to conduct controlled experiments in macroeconomics. For example, you simply cannot take half the population and apply one policy to them and take the other half and apply a "placebo" and see what the results are. The scale and ethical problems prevent such experiments.
Instead, macroeconomists like to use "natural experiments" (as they call it) that occur at discontinuities in current policies. For example, let's say that some policy has an income cut off at X USD/year. People making less than that can use the program, but people making more than that cannot. You can look at people making X-1 USD/year and compare them to people making X+1 USD/year. The slight difference in income is basically negligible, so in effect you are studying the effect of the policy, but only at a particular income level unfortunately.
Note that the difficulties using the scientific method continue to other fields like weather prediction. In these fields scientists can conduct observational studies but not experimental (controlled) studies, since we do not have the means (or even the desire) to effect the phenomena in such a way to verify or falsify some questions directly. Indirect (and far more clever) methods are still possible, though.