Tucked among the 230 blather of the Executive Order is a threatened ban on placing federal government ads on sites the government finds exercise viewpoint discrimination. Wanna know why that ban would violate the First Amendment? Read on . . .
Section 3 of the EO threatens to leverage the federal government’s significant online advertising spending to coerce platforms to conform to the government’s desired editorial position of "neutrality" 
This implicates the 1st Amendment because at its essence the government is punishing a speaker for expressing a political viewpoint. The government would otherwise place ads except it dislikes the political viewpoint reflected by the platform's editorial and curatorial decisions.
This is true regardless of whether the platform actually has an editorial viewpoint or if the government simply perceives a viewpoint it finds inappropriate. And it doesn't require that the message of the ad be inconsistent with or undermined by the site's viewpoint.
The purpose of government ads are to inform the American public, often providing critical health and safety information. They are not intended to be awards of government beneficence.
In other contexts, the Supreme Court has made clear that the government’s spending decisions can generally not be “the product of invidious viewpoint discrimination.”
The Court has applied this rule to strike down a property tax exemption that was available only to those who took loyalty oaths, explaining that “the deterrent effect is the same as if the State were to fine them for this speech.”
& the Court struck down a condition that denied CPB funds to any public broadcaster that editorialized, even if it was done solely with private finds. "The expression of an editorial opinion . . . lies at the heart of First Amendment protection" supreme.justia.com/cases/federal/…
Even when the Court rejected a First Amendment challenge to a requirement that the National Endowment for the Arts consider “general standards of decency and respect for the diverse beliefs and values of the American public” as one of many factors in awarding arts grants, . . .
the Court emphasized that the government could not “leverage its power to award subsidies on the basis of subjective criteria into a penalty on disfavored viewpoints” and the funding decisions should not be “calculated to drive certain ideas or viewpoints from the marketplace.”
By denying ad dollars that it would otherwise spend solely because it disagrees with a platform’s editorial views, or dislikes that it has editorial views, the government violates this fundamental principle & harms the public, who may need or want the government's information.
