Let's consider a person's right to vote as an example.
It's funny that you would pick the "right to vote" as the basis of your argument, because on it's face your support for such a notion is wrong if you consider the founder's interpretation of the Franchise to vote.
Specifically they did not see voting as a inalienable human Right. They in fact limited voting previleges to White Male Landowners. Now the first two attributes were I believe cultural hang overs of having White Males be the dominant ruling class in Europe. Blacks and Indians were considered, at the time, sub-human so that is why they had no Rights, however Women or non-landowning men were considered human and privy to all the inalienable Rights and yet they did not gain the "right" to Vote.
However the Landowner attribute had a very specific purpose behind it. The founders believed that a voter could not be trusted with a vote unless they had tangible interests to protect in which the success of the nation was tied directly to the success of themselves(i.e. they attempted to tie self interest(greed) to common interest(the nations well being). Land ownership was the basis upon which they believed a vested interest could be determined.
The whole idea was to prevent non-landowners from voting themselves various favors from the government (gee the wisdom there when looked at in the light of today's welfare state seems to be a down right premonition).
So I think in this case, your understanding of inalienable rights (at least from the view point of the founders) is faulty.
Now I understand the point you are trying to make that the creator bestowed, or otherwise humans have Natural Rights imbued to them, and that supposedly they can't be simply wiped away by a majority (even a vast 2/3rds one as needed for amendments). But we do indeed strip or deny various rights from Criminals, the mentally impaired, children, military personnel, and various other categories of people. This means we have all sorts of examples where either the collective people strip rights from individuals(criminals etc), or individuals suspend or trade their Rights in exchange for some gain or willing sacrifice(military personnel).
But the fact of the matter is the Constitution is, as a document, precisely that which I am describing but with a scope encompassing all citizens of the Union. It is a social contract between the People and the government outlining what Rights the people are suspending in order to form a government in which a more perfect Union is formed. The founders believed that in order to create something better, bigger, and more capable of withstanding the world pressures of the day, that a trade of Rights in exchange for mutual security, collective diplomacy, regulation of fair trade between the colonies(soon to be states), and with other nations that a contract was required that would serve as the Framework of the relationship between the People and the government.
Constitutional amendments, as I understand, are not approved by the people but ratified by the states. That makes sense to me, as the Constitution itself is an agreement between the states to assign some of their authority (derived from the consent of their citizens) to a central (federal) government in the first place.
And they believed that this contract could be further altered (including the additional succession of Rights on the behalf of the people) should 2/3rds of the people ratify an amendment to do so. And yes I believe you are correct that 2/3rds of the states have to ratify it, but the states are acting as representatives of the people. And it is why in many states should an amendment be under consideration, there is usually a general election within each state so that they have a direct count of the voters who are for/against it.
Anyhow, that is why ultimately the ban on alchohol was Constitutional(stupid but constitutional). One could certainly argue that one should have the right to drink. But when enough people believe that trading that Right in exchange for something else (I'm guessing the prohibitionists thought it would be security and stability), that they can pass an amendment, then they have
legitimately suspended that Right for everyone, as in accordance with the structure of the Constitution.
It is ultimately why I am pissed with the Anti-gun movement. You want to ban guns... fine. But have the balls to do it the correct way and pass an amendment. Instead they misuse our already severely abused Federal system to force laws down our throats which are unconstitutional IMHO(at least until they really can pass an amendment).
And keep in mind, from a practical stand point, I doubt you and I are all that far apart on our views of things, but the nuances of Rights, and their permenance is where I think a lot of Rights activists(gun, human, free speech, etc) get it wrong. They are only permenant so long as the People desire to hold onto them.
And that ultimately is the beauty behind the Right protected by the 2nd. Should a minority not want to give up this right, it the one right in which the minority, should they have the willingness to fight for it, can take it back from the majority... by force.