Do banks and credit unions accept stocks as collateral for personal loans?

the main suitable place is the place you presently have your checking account. in case you organize with the lender to rapidly withdraw the fee from the checking account they even shrink the interest on the own loan.

I don't know if a credit union would be able to do this. But many banks do, check with the business banks. We have done this with City National Bank.

For the others potential reason why he doesn't want to sell the stock:
- the interest on the loan is going to be significantly less than capital gains
- he thinks the stock will continue to increase
- he likes owning the stock.

sometimes, but theyll want to ask "if you need money, why aren't you simply selling these shares?"
they could also mention you can set up a margin account and then withdraw cash, and no formal loan or sale will be needed.

If you have stocks, why don't you sell them?
Why pay 16.99%+ in interest when you can just sell your shares?

Life seems so simple for some people.

Note that if you have paper stock certificates they will verify them and hold them.
Banks are not fools.