So far he's ignored instead of addressing all the valid points you've made, and now he's trying to derail the conversation by bringing up experimental features, which, as you say, have nothing to do with anything else.
Since he's working from his own definition of the word "is", and his own definition of the JavaScript standard, there's no way he's going to admit what he said is wrong, even though it is, and the JSX designers were 100% clear in their documentation about shooting down his mistaken idea that JSX is JavaScript.
Now that you've made that point, he's probably just going to try to derail and change the subject again, like he was just trying to do by diverting the discussion to decorators.
Since he's working from his own definition of the word "is", and his own definition of the JavaScript standard, there's no way he's going to admit what he said is wrong, even though it is, and the JSX designers were 100% clear in their documentation about shooting down his mistaken idea that JSX is JavaScript.
Now that you've made that point, he's probably just going to try to derail and change the subject again, like he was just trying to do by diverting the discussion to decorators.