And they'd be wrong. The whole raison d'etre of rights, the whole purpose, is to "secure" some good end due to us by nature. It is a kind of "debt" in the sense that we are owed something from others. If we have a right to something, then it is something others must render unto us. Only goods are owed. It makes absolutely no sense to talk about "brute rights" that are just because they are. The burden is on those who claim them to explain why they have a right to something, and that explanation is going to be one that appeals to a good that is due by virtue of being a human being.
If these people you mention took the time to examine the concept of right and had the honesty to search for an justification for them, they would see that rights are always for the sake of some good end, and an end that is due by virtue of being a human being. Take freedom, which is the ability to pursue the good as determined by human nature. A lack of freedom is an impediment to that pursuit in some way. Freedom isn't an end in itself. It is that by which we are able to pursue the good. We do not have the freedom to pursue evil. So it is with rights.
If these people you mention took the time to examine the concept of right and had the honesty to search for an justification for them, they would see that rights are always for the sake of some good end, and an end that is due by virtue of being a human being. Take freedom, which is the ability to pursue the good as determined by human nature. A lack of freedom is an impediment to that pursuit in some way. Freedom isn't an end in itself. It is that by which we are able to pursue the good. We do not have the freedom to pursue evil. So it is with rights.