(CNN) Rabbis want Kansas state Sen. Steve Fitzgerald to stop citing the Nazis and Holocaust in his anti-abortion arguments. And so does the Kansas Republican Party.

The Rabbinical Association of Greater Kansas City says the latest comments by Fitzgerald are nothing new.

In March 2017, someone donated to Planned Parenthood in Fitzgerald's name, so he wrote a letter making clear he did not agree with the donation -- and compared Planned Parenthood to a Nazi concentration camp.

Sen. Fitzgerald did NOT appreciate having a donation to @PPGreatPlains made in his honor. Just FYI. https://t.co/raCPC9b3nX #ksleg #heinous pic.twitter.com/D5AbOgRfLM

The latest episode has Fitzgerald saying Nazi doctor Josef Mengele used the same rationale as those against Fitzgerald's proposed amendment to ban scientific research of fetal tissue from aborted pregnancies. Fitzgerald says he believes Mengele thought his research would benefit mankind.

Mengele conducted many horrific "experiments" at Auschwitz, but did so attempting to prove his anti-Semitic and bigoted Nazi views. According to the US Holocaust Memorial Museum , Mengele tried to use science to show a "lack of resistance among Jews and (gypsies) to various diseases."

Now, the Rabbinical Association has had enough, and it told Fitzgerald so in a letter.

"We urge you, if you have any regard for the destroyed lives of our family members and the millions of others murdered by the Nazis, to stop using this kind of language," the association wrote.

The Kansas City Star first reported the letter's existence.

Fitzgerald told CNN while he doesn't mean to offend, he's not going to say he'll stop using the Nazis and Holocaust to support his anti-abortion arguments -- that no one should limit anyone's free speech.

Doubling down on his stance

He's fixated on his interpretation of a line from the letter, claiming the association took a pro-abortion stance in its wording of their letter: "(The Nazis') sole purpose was the dehumanization and destruction of living, breathing human beings with independent existences whom they say as inferior life."

He also told CNN, "somebody better check the party affiliation" of the rabbinical association leadership.

Association president Rabbi David Glickman says they never took a position on abortion policy and they don't endorse or oppose any political candidate from either party.

"This letter was only addressing the senator's language in comparing abortion to the Holocaust and comparing his political opponents on abortion to Nazis," he told CNN.

The Kansas Republican Party agreed with the association, telling CNN in a statement, "the two issues are very different and should not be compared."

CNN reached out to the Republican National Committee for comment but has not yet received a response.

State of the race

The state senator is part of a crowded Republican primary field that is seeking to replace retiring five-term GOP Rep. Lynn Jenkins. Although there's no clear front-runner in the primary race, Fitzgerald is among the top fundraisers on the GOP side.

CNN has rated the race to replace Jenkins as lean Republican.

Democrats have lined up behind Paul Davis, a former state lawmaker who lost a 2014 bid for governor.

Davis has out-raised all the Republicans in the race so far.