David Muir Supported by Weatherman for Using Clothespin on Jacket

David Muir's new friend has his back ... no, it ain't the clothespin he's used to bunch up his coat -- it's a fellow TV pro, a weatherman admitting he does the same thing.

Greg Dutra -- an Emmy-winning meteorologist who works for the ABC affiliate in Chicago -- took to IG to defend the face of his network's national news desk after people online roasted the star for using a clothespin to seemingly make his coat fit his hunky frame better.

The veteran weatherman posted a photo to Instagram Friday taken from behind him in the middle of a live shot ... and, his coat is also cinched by a clothespin -- a move he says is pretty standard when reporting the weather.

He tagged a couple well-known news outlets in the post ... clearly wanting an amendment to the coverage of Muir.

ICYMI ... Muir got raked over the coals on social media users earlier this week when, while covering the wildfires raging in L.A., Muir turned to point at something -- and revealed a large wooden pin on his back tightening his coat to his body.

Many saw it as a vanity move and called DM out for it ... though it's possible it had a practical purpose -- keeping the jacket from flapping about in the severe winds.

Either way, Muir decided to make a change ... 'cause for his January 9 live shot, he removed the pin and let the jacket fall more naturally -- so, he's officially left the clothespin club.