pay cash and be looked down upon?

That's pretty strange, maybe it's a social thing in his particular community.

I can see that being maybe being frowned on for purchases over a couple hundred or so, but not for small things. I think cash is much more convenient for normal items since it sort of looks weird itself (well at least to me) if you used a debit/credit card for a purchase under, say, $5. Plus, debit cards waste time with pins and waiting for approval, and credit with signing receipts. I would much rather be paid in cash as well if I were a cashier.

Now writing checks is the most uncommon thing, and as rude as I may be, I'd probably coneceal a strange look if I saw someone doing that at a supermarket or something.

Jam it back in, in the dark.