Conversation so far:
What were Havelock Ellis's views on sterilization?
Havelock Ellis was strongly opposed to the idea of castration for eugenic purposes.
Did Havelock Ellis speak out on this matter?
Yes, Havelock Ellis's publication The Sterilization of the Unfit, Ellis argued that even institutionalization could not guarantee the complete prevention of procreation between the unfit.

Question: Why was he against sterilization?
Self-contained rewrite: Why was Havelock Ellis against sterilization?