Kelly Clarkson Bird Feud: Art of Play Co-Owner Says Employees Are Getting Threats

Kelly Clarkson's bruised ego sparked her legions of fans to threaten staff at the Brooklyn toy shop that she says refused to sell her a mechanical bird ... and one of the shop's owners says she's just mad they didn't put her on a pedestal.

We got Art of Play co-owner Adam Rubin in New York City on Tuesday ... and he told us it's been a stressful 72 hours since Kelly ripped the shop for allegedly treating her like Julia Roberts in "Pretty Woman."

Adam says the negative attention has led to attacks online ... with folks demanding an apology from the store, even though Adam notes a majority of his haters have never set foot inside.

Adam's also upset that folks who are stepping up to defend Art of Play are dealing with nasty comments being lobbed at them ... including one comment involving a beloved pet and an incurable disease.

He says he never imagined the anger would swell this much ... but he says Kelly clearly did -- because she knows the power of her celebrity.

Kelly's just mad she was treated like a normie, Adam says ... though he's down to make peace if she's willing -- inviting her to a 21+ magic show held at the shop.

As you know ... Kelly tried to buy a $15K mechanical bird, but the shop says it was never for sale. When she couldn't procure it -- and was instead offered a cheaper alternative -- she bashed the brand online.