It would bother me too.
But not to the point of withdrawing my support, assuming their business has nothing to do with IT and AI otherwise.
Doing your posters with AI nowadays is the same as using ClipArt+ComicSans in days of yore.
OK, it's not exactly the same. So then I'd have explain it to them. "Forgive them for they know not what they do."
That said, I rarely support business just because it's local and small. There needs to be at least one more reason. I have seen too many local & small businesses & owners that exploit and pollute and corrupt just like their big counterparts.