Keeping borders closed restricts human freedom.
Restrictions on the right to migrate are only moral if there is clear evidence of very bad consequences. Even then it could be questionable.
What are you defending by keeping an immigrant from entering? Undue pressure on your culture? Wage protection from a more competitive foreigner?
If it's pressure on your culture, does that mean you have the right to keep blacks out of your white neighborhood as well?
If it's wage protection does that mean you can keep a younger competitor willing to work for less from attending a job interview by any means possible?
Or is it just because it's the law and the state has the right to enforce its laws? Where does the state get those rights? From its citizens, correct? The government cannot have any rights that its citizens do not possess. And no citizen has the right to deny immigrants access across a border, or do we? If yes, does that mean I can restrict you from entering my state? After all you're not a citizen of my state, or my city, or my neighborhood.
If we as individuals don't have the right to close borders, then how can the state have that right?
Or perhaps you think U.S. citizens collectively own the land which makes our nation. And through the democratic process we've transferred part of the ownership to the government. Does that do the trick? Well no. There is plenty of land in the U.S. owned by foreigners and foreign entities that do not get to vote and therefor have no say in that democratic process that transfers ownership to the government. And if the government does own the land, that means they could decide who you can invite over to your next BBQ, or your Superbowl party and that's just absurd.