'The Office's Meredith Defends John Krasinski's Sexiest 'People' Title, Says Haters Need Glasses

John Krasinski is People magazine's 2024 Sexiest Man Alive, and some people are pissed about the selection ... but one of JK's pals from "The Office" is firing back.

Here's the deal ... John graced the cover of People on Tuesday wearing a T-shirt and jeans, sitting on the bumper of a NYC Yellow cab ... and social media was instantly divided, with some loving the pick, while others bitched JK is cute, sure -- but NOT sexy.

Kate Flannery -- who played Meredith Palmer on the hit series -- tells TMZ ... she was thrilled when she heard John got the honor -- and had a feeling sooner or later he would be recognized for how hot he became for his roles in "Tom Clancy's Jack Ryan" and "13 Hours: The Secret Soldiers of Benghazi."

As for the haters saying he is more of a cute nerd -- but not THAT sexy -- KF says they need to get their eyes checked ... and watch him in something other than "The Office."

Beyond the looks, John has been crushing it on the Silver Screen over the years, starring in roles in many Hollywood films such as "A Quiet Place" and "If" -- both of which he also directed, BTW ... plus, he's married to actress Emily Blunt, and they have 2 daughters, Hazel and Violet.

Kate tells TMZ -- for the most part -- everyone on "The Office" was an unknown when the series started in 2005 ... but she had a feeling there was something special about JK. He had a certain spark, and she knew her hunch was right when he quickly skyrocketed to fame via the series.