Immigrants are immigrants just as indigenous people are just that.
There is no special EU immigrant group where everybody in it needs benefits. In fact that is just what Cameron's special deal has got rid of. He has a veto if there are too many immigrants coming in, so anyone who does not want to be swamped by immigrants had better vote to stay in the EU.
Of course, you will not do that because you do like putting all immigrants into categories, of people who should not want a better or different life, or to train and be educated in this country, then work here, because that does not fit your ideology.