It would be similar to forbidding depictions of Mohammed. Next you'll want to forbid cursing or anything that touches religion? Ironic from someone who promoted domestic terrorism. https://fstdt.com/$BVZHSPN_FD8B And what would you consider "Jesus crucifixion denial"? Anyone who doesn't embrace your particular version of Christianity? You're then into doctrinal heresy accusations.
Also, someone who doesn't believe in Christianity is not necessarily someone who wants to end it. Holocaust denial is generally promoted by neo-Nazis as part of their antisemitic propaganda. It includes other hate speech like jew marking, blood libel, etc. A movement calling to kill more innocents. Denial of the holocaust is not only a personal faith issue, and we're speaking of a recent enough event in human history that has been written about extensively by actual historians, not 70+ years-later "testimony" gospel in ancient books.
There is propaganda that is dangerous and mainstream platforms wishing to remain mainstream decide to take action when they consider it necessary for their business and reputation.
Historians evaluate that it is likely that Jesus was based on living person(s) but that stories of miracles are implausible and they understand that the formation of human traditions happened, with their literature. There also were older deities than Yahweh in human history, fertility cults and animism, etc. Also, note the difference between my reality-based argument about "actual Yahweh existence" and the promotion of antisemitism and Holocaust denial...