Is it even possible to be an atheist and/or materialist, and also believe in rights?
It's a concept, but not one adhered to. Not talking 1/2A, but food, shelter, love, aspiration/actualisation. People ought to be entitled to these things as means of survival and meaningful existence.
Rights exist, but are contingent on material conditions. Different systems have different rights conceptions not because they "agree" to have them but because they arise from the social and economic relations. This is true even if the individual morality of people differs massively from those conceptions of rights (though often people's personal morality also shifts to be more compatible.)
Now this doesn't mean there aren't universal human values. Most humans would prefer not to be shot in the head. But social and material relations can convince them to get shot in the head as a right and true thing to do, or conversely, destroy others to maintain their own perceived security.
This also doesn't mean there is no "perfect morality" given by god or nature or whatever. Maybe there is. But if you want to live it you're gonna have to accept it's not hard coded to happen while you sit around or make tiny individual gestures.
I'll share an insightful comment I found on reddit
"Ohhh I can help you with this one. Just concluded teaching this semester's course on Human Rights Education at my university.
One of the first things you'll want to read is Dembour's (2010) article on four schools of thought re: HR ontology. https://heinonline.org/HOL/Page?handle=hein.journals/hurq32&div=4&g_sent=1&casa_token=FCkqn7b8cVsAAAAA:3a1_i8KUyS4f2sDr68R719UNMNx7kO4Gg5n9fsABOuO-KKHPBzfyVgnRD6WjLE0oNNaSkKLq8Oqi
I'll start short and you can ask more questions if you like.
As all things, it is a significant debate.
Dembour argues virtually arguments take one of 4 approaches to the existence of human rights.
1.A natural approach (that rights have always existed edit: and do so simply as a fact of nature) 2.the deliberative approach (that rights exist because people/polities agree that they exist) 3.the protest approach (that rights don't exist until they are fought for and won) 4.the discourse approach (that rights don't really exist but rights language is a powerful avenue through which to make political claims)
Sally Merry is also another author who you may want to read on this issue.
Long story sorta short:
Many - like the UN - claim that universal rights exist.
Almost all recognize that, even if they do exist, they are 'worked out' or interpreted differently across the globe.
The rub sort of lies in the question: at what point does promulgating/protecting/enforcing a certain conception of what constitutes a Human Right actually begin to infringe on the human rights of others' agency to articulate/enact human rights as free people?
By and large, anthropologists and sociologists will likely ascribe to the 3) protest and 4) discourse approaches (yes, 4 is by far the most skeptical of HR).
Political scientists and IR people will likely follow thinkers like Habermas down the 2nd alley.
Actual legislators and activists are probably most likely to use the first approach."
rights are confirmed and secured by the popular terror against reactionaries