A person identifying with a different gender is rare. Changing their mind after is rarer still. In the end though it doesn't matter. Unless of course they've taken the drastic step of surgery.
What you're saying is that people should feel guilty for identifying with another gender because very rarely they change their mind later. A problem THEY not you, have to deal with if that occurs.
It seems to me that your problems with transgenders is exactly that. A problem you have.
Regret after changing is not at all rare within the group, which is those that transition. Quit obfuscating.