Assimilation has been almost impossible with levels of education (of most migrants), literacy issues in their own language, literacy deficits in the European language, being marketable for an advanced economy job, sheer numbers of migrants all at once, a high % of males between 18 and 40, crime which comes with all of this, a culture far from most European cultures, a possible unwillingness to fully assimilate on the part of the migrant, and the list goes on.
My point that those EUROPEAN leaders whom have often undemocratically forced this upon the native population are inviting what I think will be inevitable bloodshed when a critical mass hits, and/or assimilation problems remain (likely will for sure). Factor in, at that point, that both sides will eventually become polarized (predictable), and because of the rather predictable outcome, those leaders are not serving humanity. Just the opposite.