You and I agree. Sorry if I didn't make that clear, but the way I read the post at the top of this thread, each claim could be backed with appropriate evidence for and against (as Feynman says every scientist's duty is). For a sufficiently well defined situation X, the claim that "Y is the most appropriate solution for X" can and should be tested appropriately.

The "appropriate" amount of testing would also depend on the situation X. The 'difficulty of observation' may be a factor here, but is not the only one. If the situation doesn't require 'hard' evidence (e.g. the consequences are minor) that's fine, but I wouldn't say any of the above examples fall under that category, and people making decisions based on 'soft' evidence should do so knowing that it is what it is.

Also, whether there is or isn't a strict ordering, dependence on the individuals, or a silver bullet would all be facts turned up by sufficient application of the scientific method. This relates to Feynman's points on how it's necessary to do experiments where you "don't learn anything new" and again, how every scientist is ethically bound to report results that contradict their theory.