Ireland is part of the EU.
The EU controls its borders.
If the UK is not part of the EU, then there needs to be border controls between the EU and UK.
Its like saying the United States is forcing Canada to have border controls.
No what I'm saying is when the UK is sovereign and can control it's borders only one party is the one forced to have borders that being Ireland and it's not by their choice possibly but by the EU.
There is no need for a border wall between EU and non EU countries. Denmark joined EU long before Sweden and we had tonally open borders back then, and Norway is not a member of the EU and we have totally open borders between Norway and Sweden.