First of all, I think Hooda is taking the very first sentence as a bit of a sub-headline, and really means the first full paragraph. So:

When Donald Trump took office two years ago, I and many others began sounding the alarm — not out of partisan worry but out of concern for democracy.

The first phrase in that sentence is true. Alarms were sounded. The second is false. Partisan worry was absolutely the primary concern for most of the members of the talking head set.

Trump, we argued, was an existential threat to the republic.

True. That argument was made.

For the first time in American history, the president of the United States was an authoritarian-minded demagogue who viewed checks and balances as outdated nuisances rather than sacred principles.

False. Right off the top of my head I'd say FDR and Nixon were equally disdainful. There were probably more.