There are two problems with this kind of rhetoric.
First, as everyone and their cousins have been lately observing, it’s not at all clear how U.S. interests are advanced by declaring behavior to be “unacceptable” when we have no intention of doing anything about it. (There are notable exceptions — ask Muammar Qaddafi — but in general, most activities condemned by the United States as unacceptable continue to this day, or, to the extent that they have stopped, they stopped with no credit due to us.) Iran routinely kicks sand on U.S. red lines, as does North Korea. Then, of course, there are all those “red lines” with Syria.
If we aren’t willing to take decisive action to stop the Syrian government’s appalling activities, what can it possibly mean to thump our chests and claim to have a red line? “Men,” wrote Machiavelli, “must either be caressed or annihilated.” Teddy Roosevelt proffered similar advice: “Speak softly and carry a big stick.” We speak loudly, and though we undeniably carry a big stick, we mostly seem to flail about with it at random.
This isn’t an argument for using military force in Syria, or Iran, or anywhere else — maybe the use of force is justified and useful and maybe it’s not. But if we in fact intend to accept the “unacceptable” and tolerate the “intolerable,” we would be wise to develop a different and more nuanced vocabulary.
There’s a second and less frequently noted problem with our absolutist rhetoric. It’s just obnoxious — and its sheer obnoxiousness makes it dangerous. The rhetoric of “unacceptable” and “intolerable” risks generating and reinforcing the very bad behavior we’re trying to stop — not just because each empty threat further reduces our credibility, but because our general stance toward the world has become so hectoring and schoolmarmish.