Are you suggesting people culturally removed from your own are a threat to you in some way?
I can rather confidently say that there are cultures with values that are a threat to me, my society and my values, yes.
Cause damn. That’d be embarrassing.
Not in the slightest.
Or are your own police not more violent to their citizens?
No. For a very long time our police was amongst the least violent in the world. Probably still is.
What is it that allowing immigrants in doesn’t improve?
It reduces the productivity of society. Most certainly on an output/capita level, probably even on a total output level. Previously we were able to afford huge amounts of support to organizations such as the UNHCR (almost 1% of GDP) - money that could be used to make the places these people are moving away from better. That isn’t the case anymore.
The solution isn’t to move everyone to developed countries, it is to improve the situation in developing countries. We can’t help with that if our country is an unstable mess of migrant gangs attacking each other and the rest of us.