It's not the shop's fault he's incompetent. They verify that he has the credentials, so blame his poor instructors. Or lack of diving in the intervening period - his instructors might have turned out a diving guru but if he hasn't dived for years he will have forgotten most of it
Now that shop-blame is out of the way... There are a few ways I could play this:
* Talk to him and determine if he feels bad about it, or if he's a dick and this gear check is beneath him.
** Knowledgeable yet lazy dick: Steer well clear and get another dive buddy (if you were paired up) - if he is lazy on the surface, he might well be as lazy below.
*** Go solo, or ask for another buddy if he was supposed to be yours, or just go have a beer (because that dive might end badly). Agreed!
** If he feels bad about it and isn't a dick:
***Talk to him and assess his skill level and knowledge. Hard to do with a practical skill - his knowledge might be ok but if the skills are poor (due to lack of use), he might still be a danger below
***** If his knowledge/skills are awful, politely tell him he should reconsider today's dive and perhaps do a refresher course, or hire a dive guide/personal DM from the shop to take him. Definitely agree.
***** If his knowledge/skills aren't atrocious: Be nice to him and help him out. Show him what he's doing wrong and how to fix it. Possibly but would be very wary and potentially treat it as a "solo with buddy dive"