AI have absolutely no problem with controlled immigration, in fact I wold go further, I think it is absolutely necessary for the well being and development of a country.
However, uncontrolled immigration is bad for the recipient country as well as being bad for the immigrant. Countries cannot suddenly spring up an infrastructure, hospitals, roads, housing, schools, Police ... the list goes on. Mass uncontrolled immigration also leads to the immigrants congregating in one are and not integrating, this too is not good for anyone long term.
Labours great multicultural experiment showed this.