It is a misstatement that the pretext for Arizona's secession was the interruption of the U.S. postal service. Here is the quote from their March 16, 1861, secession document:
RESOLVED, That the recent enactment of the Federal Congress, removing the mail service from the Atlantic to the Pacific States from the Southern to the Central or Northern route, is another powerful reason for us to ask the Southern Confederate States of America for a continuation of the postal service over the Butterfield or El Paso route, at the earliest period.
That statement simply cites a reason to ask the CSA to provide the postal service since the route goes through the CSA. That they could do without seceding. The reasons for seceding were more what you put at the first part of your excerpt. Here is the first part of the document:
WHEREAS, a sectional party of the North has disregarded the Constitution of the United States, violated the rights of the Southern States, and heaped wrongs and indignities upon their people; and WHEREAS, the Government of the United States has heretofore failed to give us adequate protection against the savages within our midst and has denied us an administration of the laws, and that security for life, liberty, and property which is due from all governments to the people; and WHEREAS, it is an inherent, inalienable right in all people to modify, alter, or abolish their form of government whenever it fails in the legitimate objects of its institution, or when it is subversive thereof; and WHEREAS, in a government of federated, sovereign States, each State has a right to withdraw from the confederacy whenever the treaty by which the league is formed, is broken; and WHEREAS, the Territories belonging to said league in common should be divided when the league is broken, and should be attached to the separating States according to their geographical position and political identity; and WHEREAS, Arizona naturally belongs to the Confederate States of America (who have rightfully and lawfully withdrawn from said league), both geographically and politically, by ties of a common interest and a common cause; and WHEREAS we, the citizens of that part of New Mexico called Arizona, in the present distracted state of political affairs between the North and the South, deem it our duty as citizens of the United States to make known our opinions and intentions; therefore be it...
If you'll remember, I mentioned to you before that Arizona had also seceded on February 3, 1861, more than a month before the document you cite. In their February 3 secession document [Source: Austin, Texas State Gazette of February 23, 1861] they do not mention the postal service issue. Thus, it is hard to see that the interruption of postal service was the pretext for their secession, since they had already seceded without mentioning it. The first secession document was issued before the formation of the CSA when they wanted to be attached to the Republic of Texas should Texas secede; the second was issued after the formation of the CSA.
The secession of a territory is not unlike the statement of a child saying which parent he wants to live with after a divorce.
I submit that while it's possible for states to secede with the consent of the other states, absolutely nothing in the Constitution supports the idea of a territory seceding.
WHEREAS, a sectional party of the North has disregarded the Constitution of the United States, violated the rights of the Southern States, and heaped wrongs and indignities upon their peopleThat's an interesting claim for the seceding touch-holes to make -- if as you say, the Arizona secession occurred a month before Lincoln took office. But that's not surprising in the least bit. Thanks again.