Define what a fundamental right is, and I will get back to you. Ultimately, with a democratically elected government (or democratically biased republic, like the US), the real deal is upholding the populace's views.
From the United Nation's Universal Declaration of Human Rights:
Everyone is entitled to all the rights and freedoms set forth in this Declaration, without distinction of any kind, such as race, colour, sex, language, religion, political or other opinion, national or social origin, property, birth or other status. Furthermore, no distinction shall be made on the basis of the political, jurisdictional or international status of the country or territory to which a person belongs, whether it be independent, trust, non-self-governing or under any other limitation of sovereignty.
(1) Men and women of full age, without any limitation due to race, nationality or religion, have the right to marry and to found a family. They are entitled to equal rights as to marriage, during marriage and at its dissolution.
There. Definition given. Tada.
See, Here is the deal with your chosen definition.
It is the result of collaborating opinions on what people should expect to have as a "right." It is arbitrary, in that many previous groups of humans have colluded in this fashion to hammer out a codex of legal doctrine that safeguards these "rights" in human history, and these groups' opinions on what those rights are and how inalienable they are have differed wildly.
That's why some groups of humans have historically given such protections only to men, or only to people of a certain ethnic background, what have you.
Ultimately, there is nothing truly "fundamental" about these collectively ascribed features that the society chooses to enshrine and protect. Unlike, say, the charge of an electron, which derives its fundamental charge from the combined partial charges of its constituent quarks, who have truly fundamental properties-- the so called "fundamental" rights derive only from debatable and arbitrary ideas created by collections of humans. In short, humans have these rights, because humans say they do. On the flip side, since this is the true fundament of these fundamental rights, they can be easily overturned by a larger, or at least more powerful group of humans, simply using force to do so. As a consequence, humans also DONT have those rights, because other humans say they dont.
This gets even more complicated philosophically, because it is often considered to be unconscionable for one group to force its views and ideals onto another group, because this destroys one of the groups, and diminishes the spectrum of the human condition. (Loss of unique cultures, et al.) Extrapolated out, this means that for the same reason it was not A-OK for the technologically superior European settlers that arrived on the North American continent to subjugate and defraud the indigenous peoples and destroy their cultures for said European's benefit-- (Under the auspices of "spreading civilization to those savages") it is likewise not A-OK to forcibly subvert the belief structures (and resulting views on what constitute rights) of other groups of humans, under the auspices of "Promoting progressiveness".
The UN charter on the declaration of human rights is just one really large group of humans telling all the others to fall in line. (or else)
The same is true of any other such legal doctrine.
What you are missing here, is what happens when two different sets of such doctrines collide. I have seen the rhetoric stated that these bodies are "Well-Established". I will counter this with other such "Well established" bodies that define rights that are to be respected within civil matters-- Namely, the quran and the levitical texts. Those are so very well established in fact, that they have outlasted the modern documents cited by nearly an order of magnitude in terms of raw time. By what power or authority does one group, with such "Well-established" rights as those created by the UN, declare that the rights afforded by older doctrines (such as religious texts) are superseded (or else)? (The answer, you will find, is military and or police power/might.)
This leads to an ethical conundrum:
Would you say that a group of religious zealots taking over with lots of guns, bombs, and other high power ordinance, and ripping up your beloved doctrines on human rights is acceptable?
If you say no to this question-- how do you justify doing that exact thing to the religious communities that forbid homosexual couplings and unions, under threat of imprisonment and violence by the state?
If you said yes to this question, then how do you justify the specific messages inside your particular flavor of philosophical tyranny over that of any other arbitrary group, since by enforcing that set of inclusive messages, you are destroying other groups, whch is the opposite of being inclusive?
This is the actual meaning of my rhetorical question to you. "can you define what a fundamental human right is?"
Naturally, since an actual exploration of that topic would have destroyed your philosophical perch, you ignored it completely.