Fox's question still stands. If most immigration is from outside the EU, why are "leavers" focussing so much on EU immigration and ignoring the larger problem?
Because for non-EU migrants we can screen who comes in and who doesn't I.e we can welcome people that have a skill the country needs etc.
The current system discriminates in favour of the EU and is wholly unjust on non-EU migrants, particularly those from the commonwealth with whom we share a history.