Breaking the rules and expecting to be validated is one thing.
if you actually intend to do it, you are depriving someone else of a chance to ride.
Even so, I don't see how cheating can be said to devalue the efforts of someone who doesn't cheat. Piss them off, maybe, but probably not, generally speaking. If I'd got round PBP fairly, I don't think I'd care at all about someone who used assistance. I'll probably never meet them, especially since they will have gone home by the time I've recovered the powers of movement and speech.
Cheating may be a problem for the validating officials but I don't think it should make non-cheaters feel bad - rather the opposite. In any case, when you tell a member of the public that you completed PBP, they are going to say, "What's PBP?" not "Ah, but some of them cheat, don't they?!"
Peter