[The disbelief is completely understandable. Unless it was an apocalypse that could be stopped by a pie-eating contest, he doesn't really seem like he'd be your guy.]

I'd say it was a fair point if the advice on the wizarding wireless wasn't listicles along the lines of:

"Five fresh new ways to charm a rich guy's wife so he doesn't kill you."

"Four sassy spring essentials that hide the blood stains."

[He mimes a prissy hair flip.]

Those are difficult - and stupid - rules to play by when you're trying to do the near-impossible, and other than the basics, like not insulting someone's obvious parentage with the milk man, we should be immune by sheer virtue of being here to help them.