New York Times climate correspondent David Gelles violated one of the key tenants of legacy lefty media: He took his activism off the newspaper page.

In a post on LinkedIn, Gelles recounted his speech at the World Economic Forum in Davos, bragging that he’d “implored a room full of CEOs, diplomats and NGO leaders to step up their urgency and begin considering truly radical political and economic interventions” into climate change.

“The hour is late, and it’s incumbent on those with the capital and the clout to start deploying the whole of their resources toward the climate crisis.”

Oops: Per the Daily Beast, several of Gelles’ colleagues suggested the post violated the Times’ ethics guidelines “by crossing the line into advocacy,” and he quickly deleted it.

The lesson here: For Times staff (and so much of modern media), advocacy belongs in your reporting, not on your social media.

Of course the pretense is of full objectivity, with no advocacy at all, but the proof otherwise is in the pieces.

Gelles has authored such articles as “Hope and Despair on a Boiling Planet,” “Is It Too Hot for Fun in the Summertime?” and “Climate Disasters Daily? Welcome to the ‘New Normal.’”

His reporting often features fearmongering narratives, breathless quotes from experts (overwhelmingly ones who see climate change as an existential danger to humankind), anecdotes from people terrified of climate change and finger-wagging at those who aren’t terrified enough.

Gelles’ beliefs are obvious, in other words; the real rule he broke is: Don’t state your biases explicitly.

Save it for your “journalism.”