All other things being equal, we ought to accept the hypothesis which best explains what we observe.
For example, which hypothesis best explains what we actually see in the negotiations of the present administration with Iran: That the chief executive does not want Iran to obtain nuclear weapons but is incompetent at diplomacy? Or that he considers the nuclear supremacy of America unjust, finds it equitable that Iran should have nuclear weapons too, and merely has to seem to be against it?
Yes, I think so too. Yet intelligent citizens consider it outrageous even to suggest the possibility.