It's a non-issue at the moment, because there are easier ways to get into the UK. If you Brexit types get your way and the border is closed, it suddenly becomes the easiest way. Unless it's blocked. So, do you want to control people coming from the EU or not? Because if you do, you need a border in Ireland. If you don't, then why they hell do you even want a Brexit?
God, it's like explaining things to a toddler.
The EU need to build it to protect their market. We apparently need to build it to protect us from those horrid foreign types. Both sides have a reason for needing a border. Please try and keep up.