The actual right to privacy is implied... most likely under the 9th Amendment. This has been a difficult one to discuss. One must remember, however, that the Constitution does not grant us our rights; rather, it restrains the government from encroaching upon our rights. This is where there is some confusion. The Constitution does not restrict our rights... it restricts the government.
Being unsure of your use of "difficult", I am not sure whether to be perplexed by this statement.
I see nothing difficult about the issue of privacy. The issue is not only simple, but easily decided - so much so that I am confident any nominally intelligent sixth grader could draw the proper conclusions.
The biggest argument against the right is made by ignorant and dishonest people seeking to gain or justify illegitimate powers over other people. The absurdity of such positions finds its apex in the "law enforcement" argument where the appeal to emotion is made. In this argument the common desire for justice is used to great advantage in gaining acceptance of the denial of the right. Justifying the violation of a fundamental human right based on the purported need of the so-called "state" or it agents to investigate crimes, real or
suspected so that justice might be served is just about the most trite, tired, clapped-out lie and excuse on the books; and it works like a charm every time.
The only legitimate power "government" has to investigate is through the observation of public behavior. No lids may be opened nor stones overturned in pursuit of evidence of guilt. I am not even sure I accept the notion of "probable cause" as engendered in the Constitution except as a very narrowly defined concept in both philosophical and operational terms. In a free society one does not violate the rights of the vast majority for the sake of apprehending the vanishingly small population of criminals. If as an investigator you cannot make a case against a suspected criminal based on evidence obtained without the aid of prying, then too damned bad. In that case the crook is better than are you and he skates. Shitty as that may seem, the consequences of violating the rights of even the most heinous actors are profound, widespread, and very dangerous to liberty. The truth of this assertion is readily observable in virtually every nation as we bear witness to the endless erosion of human rights on a daily basis. Governments caging, beating, torturing, maiming, and murdering their citizens and other enemies, real or imagined, with impunity on a scale that should appall people, but is generally tolerated largely due to the wild success of the appeals to emotion for "justice", as well as the frantically morbid fear of "terrorists" and other bogeymen.
The general state of human thinking and perception is an unfathomable mess. People are coming around, to be sure, but whether this is occurring at a sufficient rate has yet to be seen, though my optimism is not high. Perhaps worse yet, "governments" are possibly in a position of no longer needing to care whether we are in agreement with their agendas, which begs a question as to the nature of these false institutions and who, exactly, controls them ultimately.