All human beings have the same specifically human needs…
Please, enumerate them. I mean which are those specifically “human” needs which are present in each and every human being. I can only think of the list which describes ALL the living beings, namely to have some “energy” (name removed by moderator)ut and a non-lethal environment. But since “nature” does not care to provide even that minimum, all you have is an: “it would be nice to have it”-kind of “pie in the sky”.
For instance, human beings are social by nature and as social creatures need to live in community. Therefore, all human beings possess civil rights.
There is no “therefore”. Can you show that there is?
Humans are both individuals and social beings - that is correct. But from this it does not follow that there are “civil rights”. As a matter of fact, “rights” don’t grow on trees

, “rights” are
social constructs. When we talk about a “right”, it means that you will not be persecuted/punished to act in a certain manner (or cannot be persecuted/punished for NOT acting in a certain manner). Different societies provide a different set of “rights”. And to add insult to injury, many times they are unable to protect those “rights”.
Furthermore, there are
negative rights - the right to be left alone, and
positive rights - to have access to something. Positive rights always place a responsibility on
on someone else who is required to perform a certain action, or provide a certain service to you, even if you cannot “pay” for it.
I trust you will rethink your position.
If you can give some actual arguments, I will consider them.
The dissenters excommunicate themselves.
I rather doubt it. They still consider themselves Catholics, the church allows them to partake in the communion.
Easy, first agree first on the existence of a human need. The “measurement” will become relevant only to the extent or the quantity of the good required to satisfy the agreed upon need.
Not easy, but what you say still requires a list of human needs that everyone can agree upon.
If one believes that the truth in morality is singular and independent of the way people think about it then one does have a problem with multiple moral systems.
But that is clearly not the case. And wishing it does not make it happen. For example, many people (Catholics, too) do NOT believe that non-procreative sex is somehow “immoral”.
The “golden rule” like the “categorical imperative” are both empty of content and leave morality in the sphere of the subjective rather than objective.
A guideline is just that, some generic principle, which can help in the particular cases. The principle of “golden rule” is the best candidate, since it has been accepted since time immemorial. The Kantian “categorical imperative” is a relatively new idea, and many people don’t accept it.
Now, it is obvious that most of the time it is mutually beneficial to respect each other, to cooperate with each other, to help each other. But not “always”… there can be exceptions. So, even though there will be exceptions, usually the best strategy is cooperation - as the fundamental basis of a “morality” system. But from this principle only a handful “rules” will follow - and most of them are reflected in the legal system.