The Human Rights Campaign, responding to numerous queries from transgender activists, has sent a letter of complaint to Late Show With David Letterman in light of Tuesday night’s skit in which he poked fun at Obama appointee Amanda Simpson, the first trans woman appointed by a president.

The letter, addressed to Letterman with a copy to CBS Entertainment president Nina Tassler, calls the skit transphobic and says that “the punch line in your skit has been used as a defense in nearly every hate crime perpetrated against transgender people that has come to trial.”

The letter goes on to name Jorge Steven López Mercado and Angie Zapata, two transgender teens who were killed in 2009 in violent attacks.

“Your skit affirmed and encouraged a prejudice against transgender Americans that keeps many from finding jobs, housing, and enjoying freedoms you and your writers take for granted every day,” the letter reads. “We ask that you apologize publicly to Ms. Simpson and the transgender community for this unfortunate episode.”

Trans activists took to the Web almost immediately after the skit aired to express their disappointment, but not everyone is pointing the finger at Letterman. Some argue his skit was actually making fun of the narrow-minded, stereotypical response to learning a friend or colleague is trans.

Read the full letter here and watch the skit below.