If you feel comfortable enough, tell them in a very calm tone that it’s telling people things like that can cause trans people to commit suicide, and when talking to people, they should be supportive whether they agree with it or not to avoid causing mental distress. Make sure you also tell them that you aren’t trying to be rude and are just trying to give advice, and if they listen to the advice, you have just helped ever other trans person at your school, and if they say something like you don’t know what you’re talking about, tell them that if they don’t respect what students say, students won’t respect what they say, if you aren’t comfortable enough to do this, that’s fine too, but just know what others say about you doesn’t matter, they don’t know what’s going on in your head just like you don’t know what’s going on in their’s, this may not be an easy thing to get in the mindset of, but once you do it helps