Remind me of the times in the 18th, 19th and 20th centuries when people had leisure time to quibble about this garbage-think.
It is not possible for mammals to change their sex. That is reality. To surrender ground on the issue of something that is REAL is to lose.
Part of the way cults work is to make their new adherents say things that are not true. Eventually the brain begins to believe they are true.
It is hitting us on every side from "change your sex" to "humans cause global warming" what ever someone feels is reality even if it is not.
Word usage defines what we believe reality is.
The usage of "change their sex" means that you concede the fact that it is possible for them to do so. That is giving ground and buying in to their unreality. Now you are saying that you want to prevent people from changing their sex.
It is not a matter of preventing them, reality has already done that and is not subject to laws passed by any legislature.