You say that like it proves your point, but it’s the opposite.
Minorities exiting NI don’t prove that NI was a post-racial utopia. Especially if they’re avoiding an open culture of anti-immigrant and minority hostility, that included techniques of ethnic cleansing, and that’s how NI was kept 99% white. You think that happened without anti-minority violence? Do you think every Pakistani kid born in Belfast was able to stay?
Low incoming immigration levels don’t guarantee that people aren’t initiating violence based on their racist anxieties. “Anti-immigrant violence” can happen in places where there are no immigrants in reach at all, as long as you have hopped-up bigots and something to hit.