Imagine inviting a guest to your house for dinner, and them liking your house a lot and deciding to just move in permanently. Are you then expected to encourage them to put their name on the lease (i.e. become a citizen)? I don't think so.
I don't think I support the concept of a long-term "guest" with no rights, so I don't think it's wrong that such rights exist. That's what countries like Kuwait or Dubai do, with long-term "guest workers" who don't have legal rights. If someone has lived and worked here (Denmark) for 5 or 8 or 10 years or whatever, I think they should have legal rights on that basis. Much more so if they were born in Denmark; and doubly that if their parents were born in Denmark too, so that it's been two generations since they were immigrants. What is the alternative in that case, deport someone who was born and raised in Denmark to a country only their grandparents were actually from, and whose language they don't even speak?
Here's how it went down. First, Germany slaughtered and exterminated millions of people, invaded tons of countries, destroyed their infrastructure, commited heinous crimes, etc. What we know as World War II.
After the end of the war, West Germany, as a valueable ally of the West against USSR, got all kinds of help and special treatment to rebuilt its economy. And they started a program for bringing in workers from places they invaded and decimated, like Greece. Those workers, like the involuntary "arbeit mach frei" workers before, were brought to serve as cheap immigrant labor, under exploitative conditions, to assist the very people that had unprovoked invaded their countries and killed their relatives and fellow citizens a decade or so ago. The guest-workers, besides being exploited with lesser wages than Germans and fewer opportunities for advancment (like b-rate citizens) they were also treated with extreme racism and prejudice.
Now, the problem of the Germans (the "they overstayed their welcome") was that these people didn't just disperse when they were done with them, but instead felt that those hard working years in Germany gave them a right to stay and be integrated as full citizens.
Such nerve, huh?
If I burn down your house (and kill your cousin and your Jew neighbors), and you or your kid, starving, accepts to come work for my company, and I treat you like shit on top, that doesn't make it OK in my book.