The best part of libel/slander/defamation is that you do not have to believe that the comments are negative. You just have to prove that 1) the person making the statement intended to harm you and 2) that you suffered harm as a result, and 3) that the statement is false.

There’s some more nuance on a case by case basis, but like Tolstoshev said, this seems pretty cut and dry. Even if the majority have no issues with trans people, there are some - and this official was speaking to them with the intent to negatively impact this person.