>The contract is based on reason

Objectively, it isn't. You want it to be. But what binds us in real life isn't. Or was it just emanantly reasonable when we slaughtered millions of muslims in the last two decades? Is decades of blockade on Cuba reasonable? Or our alliance with Saudi Arabia and active contribution to their genocide, over our petroleum concerns? Is it reasonable that people may be bankrupted through no fault of their own, by medical emergency? Or again, that the guy who picks your abundant avocados is not granted his own? That our wealthy buy their politicians? That our planet is being sacrified for fleeting monetary gains? None of this is reason. The obligation is not to law, our obligation must be to break and reshape law in service of a genuine human interest.

>someone's identity (like class)

Class is not an identity. You belong to class regardless of how you think of yourself. The proletarian, working class interest is uniquely singled out because workers actually constitute the majority of global humanity, and is thus the best class interest to serve as a ruling class, as self rule of the class ruling itself.