You have to borrow stock before shorting it... that's a rule (or...

You have to borrow stock before shorting it... that's a rule (or at least, you have to have arranged an irrevocable right to settlement prior to selling). If you don't have that, you're naked shorting, which was a naughty and annoying practice prior to the GFC, which became a highly illegal one after the GFC for obvious reasons.

As to the ethics and issues of whether asset owners should lend out their stock to shorters, there are arguments pro and con. Norges Bank has one of the biggest sovereign wealth funds in the world, so they wrote about it back in 2016. It is worth a read and some things you'll approve and disapprove of probably. https://www.nbim.no/en/publications/asset-manager-perspectives/2016/the-role-of-securities-lending-in-well-functioning-markets/