I agree with Clodia, there's no way to rationalize that Cato could occasionally go right off the rails in terms of the mos maoirum, of which the fact that a Roman citizen could not be executed without trial was a foundation principle. Only the fact that the Senate had voted the senatus consultum ultimum at the time of Catiline's conspiracy, gave any chance to a prompt execution of the conspirators. And even THEN, it had never been done before, so Cicero was going right against the mos maiorum in even suggesting it (as Caeasar pointed out, via Sallust).

I think that, after the Civil War, and as autocracy grew in Rome under Caesar, the Triumvirs, and Augustus, Cato was turned into an "instant Republican hero" with all the reverence that implies.... his human inconsistencies and weaknesses wiped right out. Otherwise, no one could ignore some of his major inconsistencies.