I'm an English teacher and I'm not that superficial about peoples' grammar. You'd seriously write off someone because they used "less" instead of "fewer"? Sounds like an excuse to get out of meeting him rather than a real issue. I could understand if everything that came out of his mouth was poor grammar or if he couldn't write a coherent sentence, but just this?

Whatever you do, be careful. Do NOT go in his car alone. Meet only in public places for awhile. Enjoy yourself and try to get past your grammar-snob issues.