fatpanda,
well buddy here is the problem with that rationale. firstly they arent the only ones who will do this work. secondly you can only have so many unskilled workers around before you have a overflow. now when you have to many unskilled workers around there becomes no work. thus alot of people filing for benefits such as welfare, unemployment ect. now instead of working and contributing it comes into a situation where they are taking away from it. and thats exactly whats happened now for many years.
now if these illegals had some skill and could be a doctor, or do a job that needs to be done such as healthcare workers, firefighters, ect, then id be all for allowing them over without having to be a citizen. but since many are unskilled and wont assimilate to the language then its pretty hard to accommodate them.