Start with these premises:
- A (human) community is obligated to supply those of the basic needs of its members that can be met, unless perhaps these members have freely consented to not having these needs met.
- It is not permitted to require anybody to have sex, absent a free promise from the requiree.
- If a community is obligated to provide A to x, then it is permitted for the community to require one or more of its members to provide A to x.
- There is at least one community where there is at least one individual who (a) is capable of sex; (b) does not have sex with anyone; (c) has not consented to the state of affairs in (b); and (d) nobody has promised anything that entails having sex with this individual.
- Basic needs are the same for all members of all (human) communities.
- Therefore, sex is not a basic need.
Note 1: What if we replace "sex" with "companionship" or "friendship" or "the provision of food"? Then I think we should deny the analogue of (2).
Note 2: Plausibly, someone who sees sex as a basic need is thereby likely to see it as a right and entitlement, and hence to have a resentment towards the persons who do not fulfill that basic need when they "so easily could", as he or she might say. There is, thus, very good reason for society to attack the idea that sex is a basic need.
Note 3: In the above, I was thinking of basic individual needs. Might not sex be a basic need for the species as a whole? Yes, it is. But as the species is larger than the community, just as not every member of a community is individually obligated to provide for every basic need of the community, so too not every community is obligated to provide for every basic need of the species. Moreover, apart from God (see Note 4), there is no authority that coordinates what basic needs of the species each community needs to meet.
Note 4: The quantifiers in (2) are restricted to fellow human beings or at least to fellow creatures. God has the authority to command a particular couple to marry, and to consummate the marriage.