Immigration both nationally and internationally

I wondering if someone explain the following points in relation to migration, economics and society. I have had the fortune to travel and work in some amazing countries and hence meet some amazing people. I have also enjoyed been to these other countries and wish them the best in the future. I personally think migration is a positive attribute but at the same time I do not want it abused by other interests to the detriment of society or migrants themselves. Whenever the subject of migration or emigration came in some of the conversations, the views I heard were quiet confusing. There seems to be some serious brain washing going on with relation to this whose ultimate purpose I have yet to fathom out but I must admit I not done my research or am no expert in this matter or its underlying causes or symptoms.

1) It seems any person whom wants a civilized and rational debate on this subject is considered a racist. Well with history one would one understand such a view but going from one extreme to another is certainly not the answer.

2) Certain sections of societies in some countries want excessive immigration in order to provide cheap labor for certain business interests. Now this observation must be taken in the context that this is what it seems on the surface but if someone could explain that this is incorrect or to a piece of research which clarifies this point I would be grateful.

3) Some conspiracy theorists point out that migration is a tool to essentially destabilize whole communities. This leads to confrontation within communities instead against those whom are corrupt and milking the system. This in turn makes these communities easier to control; the gradual taking away of power from communities to seemly ever larger centralized entities whether these be federal institutions, certain international financial organizations etc. Whether this is true is unfortunately not black or white and very debatable.

4) Then there is the argument that migration can only fill jobs that the indigenous population are unable to fill or unwilling to do. This seems to be very true that certain professionals or trades will always need a quota of migrants in some economies. As regards other jobs such as catering or security for example; I do not know. Do we start some sort of national service to fill these jobs or simply let market forces dictate supply and demand to these positions? But then you have the knock on effect to tourism and other areas. Again I am naïve to the basic economic principles at work here.

hope you find some answers here