dont agree with you - Coogan's Bluff is no one of the very goods - but its still a classic and great entertainment - about Don Siegel : no film he directed is realy bad!!
Depends what we mean by "really bad" - something you would give zero or one point out of ten? (I've rarely seen anything that bad by anybody, actually). In that case I agree - all Siegel films I've seen earn a few at least. Even the most embarrasing to watch due to weak stories and incoherent direction, as Coogan's Bluff or Two Mules for Sister Sara, or just forgettable as Madigan, still have entertainment value. But they are far below the abilities of their makers.