I agree that there is a parallel. The scale was much larger in Tet, but the Hamas "offensive" is in a number of ways quite similar. There was a massive "indications and warning" failure by the intelligence community; the assault was initially successful in seizing ground and inflicting massive casualties; and conventional forces eventually overcame the enemy. Containing the much larger offensive in Tet it took weeks, inside Israel it took about 72 hours.
In 1968, the press, led by Walter Conkrite concluded that war could not be won. That conclusion was reached in spite of the fact that the Vietcong were destroyed as a meaningful combat force for the remainder of the war. The North Vietnamese regular units were used sparingly during the offensive to preserve their combat power.
There have been dozens of books written about Vietnam, but I think there is a general consensus that a constant stream of "we're making progress" reports from the American leadership in Saigon seemed to be made a lie by the offensive. The country was growing weary of the war, and the offensive seemed to indicate the North Vietnamese and Vietcong were gaining strength rather than being defeated. In that environment, any objective assessments from the battlefield were discarded by a then thoroughly skeptical press. We still have to await the eventual press reaction to Israel's coming ground assault into Gaza. However, Tet offers a clear warning.
The parallels pretty much end there however. Israel does not have the luxury of withdrawing and Gaza isn't going anywhere. For nearly fifty years, Israel has shown great restraint and allowed first the PLO and then Hamas a large degree of self-determination in Gaza. I am certain the coming incursion will be massive and will likely rival the fighting for control of Fallujah.
This morning it was announced that the crossing point from Gaza to Egypt had been reopened and that Israel was encouraging non-combatants to flee. I have no doubt reporters will be offered the opportunity to see any number of grieving Muslim mothers and wives once the Israeli counterattack begins. Taking a chapter from ISIS, Hamas may publicly murder their hostages. Unlike the US, I sense that Israel intends to carry through and defeat if not exterminate the Hamas organization. I suspect they will be immune to any press criticism for a while to come.