And that is different to Sumter how? It seems that in either case the opposition was suckered into acting, or worse into a position of being claimed to have acted.
In neither case was the opposition "suckered" into anything, any more than President Roosevelt "suckered" the Japanese into attacking Pearl Harbor.
By the way, just so we're clear on this: I believe and have for years argued on Free Republic, that President Roosevelt did, in effect, "sucker" the Japanese into attacking Pearl Harbor, because that was the only possible way to get the United States into WWII in time to save the Brits and any semblance of western civilization in Europe.
But "suckered" or "un-suckered" doesn't matter.
The facts are that the United States in 1941 committed no -- zero, zip, nada -- acts of war against Japan, while the Japanese attack did in fact create a state of war with the United States.
The same is true of Fort Sumter in 1861, except, except that there was no possible "suckering" involved, since Confederate President Davis had already ordered preparations to assault Sumter, even before Lincoln's inauguration!
Davis was prepared for, and threatened, military assault on Sumter -- a clear act of war against the United States -- regardless of what Lincoln had said or did.
Lincoln merely allowed Davis (as Roosevelt "allowed" the Japanese) to carry out military attacks, creating states of war, which Confederates (and Japanese) believed were absolutely necessary for their own survival.
So Sumter and Pearl Harbor started war, and all the rest -- including Unconditional Surrender -- necessarily followed.
As for Lyndon Johnson's Gulf of Tonkin Incident -- there was an actual incident, in which North Vietnamese forces did attack US Navy ships.
Also, "Suckered" or "un-suckered", North Vietnamese were in fact assaulting militarily their neighbors to the south and west, including US forces sent to help those people.
Indeed, by August of 1964, about 150 US military had already died, and hundreds more wounded, in the Vietnam conflict.
So Johnson's decision to request authorization for limited war was, he believed, both reasonable and necessary.
The veracity of reports from the Gulf of Tonkin were irrelevant to Johnson's, and even Congress's, overall thinking.