How old is your daughter? Is there any genuine basis for concern about your daughter's sense of sexual identification? Are transgender or sexual issues causing your daughter any actual problems in her life? Is your ex hypersensitive to these issues?
Unless this is causing problems for your daughter, it is not abuse.Your ex' education session may have been well meant, but ineptly handled; or, if you are relying on your daughter's report, it may not be accurate. A talk with your ex about this probably would not hurt if you are on speaking terms. You could hear his concerns and take it from there.
Can you deal with it simply by having a talk with your child about these questions and how people relate to them? It is an opportunity to talk with your daughter about sex and gender issues in general, and the range of social thinking about them.
DISCLAIMER: The forgoing comment is for general educational purposes only, and is not legal advice upon which the reader may rely as the commenter has no actual knowledge of the facts of the case, has not interviewed persons or examined evidence, and has not researched the applicable law. The comment is based only on the facts provided, which are extremely limited, and may or may not be true. Complete defenses may prevent the success of any claim. Competent legal advice should always be obtained before taking any legal action or filing suit. Readers employ any information provided herein at their own risk.