rich countries should have strict immigration controls to stop people from poorer countries enter

People leave their countries from different reasons: some are looking for better education, some are looking for political asylum, some move to e with their loved ones. But what they have in common is search for better future.
However, not all the countries have their door open for immigrants. Most of the developed ones have strict immigration laws that prevent overpopulation from the 3rd world countries.
That makes sense. As once they give citizenship to everyone, there will be no young people left in poor countries, and that means no future, no development. Young people-as they are the ones who immigrate in most of the cases- should think how to make their country better, they should think about what they can do for the country and not vice-versa .
Just look at Mexico, for example,- tons of people leave heir country to work in USA -legally or not. This leaves Mexico with no bright future-corruption and degradation become common thing. On the other side, in USA, those immigrants make a huge damage to economy: taxes are not being paid and most of the jobs are taken from the native americans.

On the other hand, the statement that all immigration laws should be strict is not 100% fear.
Let's imagine a very smart scientist, who tried to improve the future of his country, but government didn't care, they didn't finance his work. It means that his native land doesn't need him, which is very sad. In this case rich countries should leave the door open for people like that, who want to make the world a better place.

People should remember wise proverb-the grass seems greener in the places we don't live. The meaning is-some people can travel all their life and never be happy. So the most important thing is to find the meaning of the life and follow it. Then you can be happy on any land.