While this exchange between the writer and the store employee is pretty silly for reasons others have expressed, I do like to buy new whenever I can.
It's nice to know that devs are seeing the profits (especially if it's a digital download purchase).
I avoid used if for no other reason when buying physical media for my collection that I can't stand visibly "handled" game cases/manuals.
If it's absolutely unavoidable only where I can inspect the merchandise and almost never at Gamestop where their god-awful price labels almost always damage the game sleeve and/or paper insert.
When I do buy PS3 games used I'm actually a big fan of buying GameFly's used stock. BluRay discs are nearly impossible to scratch, they price high-profile stuff under $20 pretty quickly (almost always months before the same titles drop that low at GameStop) and you always get a mint-fresh case & manual that was only ever opened and shelved for storage so DLC offers included are typically still in-tact.
And I can count on one hand the number of games that I've purchased for my collection in the past 20 years that I've sold/traded in.