Here is a valid argument:1. At least barring commensurate reasons, it is wrong to act in such a way that one will acquire a basic and serious human responsibility that one does not plan on fulfilling. (Premise)2. If one consensually reproduces, then one acquires a basic and serious human responsibility of parenthood for the offspring. (Premise)3. Anonymous sperm donors consensually reproduce the offspring that comes from their donated sperm. (Premise)4. Therefore, anonymous sperm donors acquire the basic and serious human responsibility of parenthood for the offspring. (By 2 and 3)5. Anonymous sperm donors typically do not plan to fulfill their parental responsibilities towards the offspring coming from their donated sperm. (Premise)6. Anonymous sperm donors typically lack reasons for the donation commensurate with the acquiring of unfulfilled parental responsibilities. (Premise)7. Therefore, typically, sperm donors act wrongly. (By 1, 4, 5, and 6)I suspect it's sound, too.
Please also read the discussion that followed this entry. Alexander Pruss raises some very good points, and argues them very well.