People should stop using immigration to argue for brexit because it's a nonsense argument.

Leaving the EU wouldn't effect our border controls, because they aren't set by the EU.

The UK isn't part of the "Schengen Area" of countries without mutual border control. The UK has control over its border policy, despite what brexit campaigners claim. It is the UK government that chooses to implement border policies which are regarded by some as "too lax", and then, sometimes, chooses to blame the EU for it.