I'm sorry but this shouldn't even be a thread, but because people have a warped mentality and understanding of the word "illegal", there somehow needs to be a discussion to fix the mentality that has been wrongfully indoctrinated into our children. I blame the illegal/dreamer children filled public schools.
Of course someone illegal in a country should be kicked out. It's in the title of "illegal". They are illegally within an area, just how someone can be illegally within your own property. It doesn't matter if someone doesn't do something wrong and obeys the law. Say we have someone like that, they are illegal in the country and are not harming someone. How do they get money? They can't work in a legal sense.
Do they just have a child and then rely on welfare until their anchor baby can work? Of course they do, and that uses up tax dollars that the citizens and legal residents work for. Do they just work in an illegal under the table job? Of course they do, and that simply ditches taxes and enables others to do the same.
So this is the situation: one is taking tax money while the other is not putting in tax money. If this is the only situation possible(which it is, unless they want to do ID theft, which is an illegal act), then they are only taking from the country and not contributing. I am not just talking about the US and Mexico, or a European country and Muslim refugees. This can relate to any country around the globe that has a government regulated welfare system and use taxes to support it.
It is very simple to avoid being illegal within a country: apply for a visa and get a job. College education in other countries allows us to go to another country and education. Work permits allows us to work in another country. International marriage allows us to marry into a citizenship. Buying property and being good with business or education allows us to show a worth towards another country. Hell, anyone can apply for a country's visa lottery.
This is how any problem involving immigration is solved: create a good relationship with a country and your people can easily immigrate to that country. Have your people flow into another country legally and normally, in accordance to that country's demand and ability to hold, and that country will be less resilient and allow more legal immigration.
Cause less problems, bring more benefits, enjoy a better relationship. This goes for countries, groups, religions, individuals, and all the way down to the lowest reach of the animal kingdom.
Somehow, someway, only humans managed to make something as simple as a "relationship" overly complicated to the point it gets flipped ass backwards. Enjoy yourself and eat pussy.