the general problem you have now is that the idea of the nation-state applies only to those not in the ruling classes. you have a global capital system where money has no borders to cross and can move instantly, anywhere. Labor, on the other hand, has no such mechanism. And even if there were a global agreement to erase borders and a recognized right of free movement around the planet, it would be a right most could not afford to exercise (which begs the question, would it then be a right at all? Or a commodity?).
A stateless planet is an abstraction only a relatively affluent person can love. there is a real cost to movement, and as such, border controls are at least necessary in any society determined to manage its own economy. It's no coincidence that Brexit-type sympathies are growing quickly, as the lowest social rungs understand their total disadvantage in a world where only some can move towards work while others are bound by their terrain.
So yes, I think right now, borders are more than necessary. They are vital. Even though my path getting there couldn't be further removed from the cultural supremacy reasoning of the right. As long as we are forced to live in a system with a massive reserve army of labor, any addition to that already enormous force further disadvantages workers. I find that unacceptable.
Having said that, it's equally vital to work hard towards stopping capital from disrupting the peasant political economy to the point where they are driving others off their own land and forcing them to take the chance to flee to the few countries willing to accept them as replacement labor for the domestic force.
It's a recipe for worker division and hatred, as one group is pitted against another: both victims of the same drive to profit at all costs.