> Ok, so then transracial individuals[1] should be believed as well?

I mean, "race" is a social construct too. There's nothing biologically different about a black man from a white man. It's a collection of cultural, historical and visual cues society imbues with meaning. So... in a way, it's got a lot in common with gender.

> What about those that identify as inanimate objects[2] or animals?

Yep.

> If we accept self-identification as an inanimate object should others be allowed to treat that person as such?

If someone earnestly identifies as an object, that's their prerogative. But no, others don't get to treat them like furniture or property because consent and dignity still apply to them. Identity doesn't override someone's right to safety, and it doesn't give others license to dehumanize, even in a twisted manner of affirming them.

And, as someone with an occasional spirit for some BDSM play, I am familiar with treating people like objects in a way that is edifying without being harmful to them.

Edit: It feels like you're trying really hard to find an edge case in self identification where it could be used to cause harm, as though the actual, current mechanisms of identity as imposed by society aren't also doing that. Yes, someone could use self identification to do something shitty. That is not unique to this concept and in fact this, and a variety of others, already have plenty of holes wide enough to drive a truck through to accomplish the same goal.

If your standard here is a system which is objectively verifiable, you will not meet it at any point. All of this is subjective because it all ties into the subjective experiences of individuals and the subjective analysis of systems and other individuals. There are no clear cut answers and there never will be, it's subjective turtles all the way down.