So this will be a bit of winding road, but stay with me.

Your question asks about Debs, but it actually starts a bit earlier, with a similar case that, in fact, is used by the Court to say "we've pretty much answered this question" for Debs.

In Schenk v United States (1917), the Court considered another socialist charged with subverting the war effort. A man named Charles Schenk was convicted under the Espionage Act of 1917 for distributing pamphlets encouraging men not to honor the draft. Specifically, section 3 of the law says:

Whoever, when the United States is at war, shall wilfully make or convey false reports or false statements with intent to interfere with the operation or success of the military or naval forces of the United States or to promote the success of its enemies and whoever when the United States is at war, shall wilfully cause or attempt to cause insubordination, disloyalty, mutiny, refusal of duty, in the military or naval forces of the United States, or shall wilfully obstruct the recruiting or enlistment service of the United States, to the injury of the service or of the United States, shall be punished by a fine of not more than $10,000 or imprisonment for not more than twenty years, or both.

In a unanimous, landmark decision, Chief Justice Oliver Wendell Holmes Jr. writes an opinion that pretty unequivocally says that Schenk's activities are actionable by the government under the law in question. He points in his decision to what has, somewhat incorrectly, been referred to as the clear and present danger test.

Holmes did not intend for the “test” to be applied to this specific case, and SCOTUS never directed lower courts to use it in rulings to determine the constitutionality of governmental actions limiting speech. Regardless, the notion he expresses is that any act by the government to restrict actions presenting a clear and present danger to bring about substantive evils that an act of congress has sought to prevent for the safety of the country, are not protected speech. Sorry for that sentence.

This points to an important distinction that many Americans don't realize: your free speech famously stops at dangers to the public welfare like yelling "fire!" in a crowded theater (which is in Holmes's very opinion), but it also stops when you endanger the welfare of the broader public. As this law was conceived, this includes interfering with the draft. As we’ll see later, the interpretation of broader dangers to the public welfare will eventually incorporate temporality.

Holmes was a pragmatist and a progressive, two closely related ideologies. Together they mean that the government should try policies out that reflect the desires of the public and continually reform them based on what works and how the demands of the public changes. He broadly trusts the public to know itself and sees the government as the instrument meant to help them serve their interests. He believed in deferring to the political branches of government on political issues, i.e. it is Congress’s job to make laws within the confines of the Constitution and it is the President’s job to enforce the laws within the confines of the Constitution. But he did think as well that the Courts, in their interpretations of the Constitution, should be receptive to the desires of the public. So when something like Schenck came before him he saw Congress as representing the will of the majority to effect the public welfare. Though he would caution against limiting speech that did not materially present a danger to the public’s safety, he saw the law as a legitimate balance between the individual’s First Amendment rights and the political branches’ rights to legislate and enforce. And he thought that the public, in electing these legislators who passed this law and related others, had said their piece.

These may seem like unremarkable notions, but they are not by any means universal understandings: many justices have and do consider the rights of the individual to be paramount, and see the Court’s duty as circumscribing the actions of the government very closely. Others believe/d the Court serves a more direct role in determining how existing congressional legislation should be interpreted differently to keep with changing legal understandings or how the enforcement powers of the president should change for the same reason. Holmes believed first and foremost in an abstracted public, something I highly recommend John Dewey for further reading on. But suffice it to say that Holmes subverted the rights of the individual to the will of the public up to a point, and thought it was Congress’s job to be the branch that was a mouthpiece for the public and the point at which the public’s will is transformed into workable policies that realize those ends.

But back to your question. Debs is charged for the same reason as Schenck just a few years later: he makes a series of carefully worded speeches, hoping he won’t befall the same fate as Schenck. When he does, he appeals his case all the way up to SCOTUS. Holmes’s opinion for the Court essentially says, “we won’t discuss this at length because the facts of this case are not significantly different from the case we just decided in Schenk.” So Debs’s conviction is upheld and he runs for president, again, from jail. Much of Debs’s sentence was, however, later commuted for political reasons.

So this is one part of why you could not be charged like Schenck and Debs were: there is no draft, and both men were charged with subverting the war effort by interfering with the draft.

But moving on to the latter half of your question, you are mostly right that you could not be charged with such a simple act of broadcasting publicly your disapproval for the war. And that relates to another, more stridently laid out test by SCOTUS in Brandenburg v Ohio in 1967. Brandenburg’s per curium opinion, which is a majority opinion that is issued by the Court and not specific authors, establishes the “imminent lawless action” test to determine whether the government can limit speech that incites violence or other crime. It essentially says that an act must be both 1.) directed to inciting or producing imminent lawless action and 2.) likely to incite or produce such action.

This ruling immediately cast Schenck into doubt for the simple reason that mailing anti-draft pamphlets or making anti-draft speeches or saying “Just so you know, we’re on the good side with y’all. We do not want this war, this violence. And we’re ashamed the President of the United States is from Texas.” to an ally in wartime, that these actions are not likely to produce imminent lawless action.

So while your fans might drive a bulldozer over your CDs, the President for whom you’ve claimed shame and whose war you’ve just subverted very publicly during wartime on the international stage will simply shrug his shoulders and reaffirm that he believes it’s your right to say so. You could also get into arguments over how much strict textualism has grown in popularity with conservatives of various stripes, but this gets a bit beyond my expertise. But suffice it to say that it’s not entirely an accident that someone like Bush would feel the literal word of the Constitution is good enough reason that what you said is ok.

The broader lesson I think we should pull from things like this is that, far from carved in granite and sealed off in a vault somewhere, the Bill of Rights, and perhaps most of all the First Amendment, is embroiled in a constant process of reinterpretation, restriction, inflation, and outright redefinition.

So get out there and publicly decry the war effort. Or don’t. And maybe check out the Dixie Chicks' new album... they made history with an offhand remark.

Sources: Burns, Kevin. "Testing Holmes: Pragmatism and Judicial Tests in Holmes' Free Speech Opinions," Constitutional Studies 5 (2019): 81-106

Cornell Law School. “Brandenburg Test.” https://www.law.cornell.edu/wex/brandenburg_test.

Frankfurter, Felix. Mr. Justice Holmes and the Supreme Court. Cambridge, Mass: Belknap Press of Harvard University Press, 1961.

(note that this is written by Felix Frankfurter, himself a very senior Associate Justice at the time of publication)

Lynd, Staughton. “Brandenburg v. Ohio: A Speech Test for All Seasons?” University of Chicago Law Review 43, No. 1 (Autumn, 1975): 151-91.

Stears, Marc. Progressives, Pluralists, and the Problems of the State: Ideologies of Reform in the United States and Britain, 1909-1926. Oxford: Oxford University Press, 2002.

Suggested Reading for Pragmatism-Progressivism a la Holmes:

Dewey, John. The Public and Its Problems: An Essay in Political Inquiry, ed. Melvin L. Rogers. Athens, OH: Ohio University Press, 2016.