Reasons behind incidents of illegal immigration

I believe there is a social reason behind any incident of illegal immigration. The primary reasons are either poverty or aspirations of a better future. All the immigrant people I have met in America have told me a more or less similar history of their immigration. So, the question is, why should such an immigrant indulge in criminal activities. There is no logic in thinking that such a person with such hopes and aspirations, after coming to a sanctuary city where he/she has no need to fear of persecution regarding his/her immigration status, then turn into a criminal just for the sake of it.
Following this logic, I believe that the cases of illegal aliens committing criminal acts are exceptions beyond generalizations. Also if we take the statistics of total criminal acts that occurred in the same period of time, I am sure there will be an equal number of crimes committed by people of our own country as compared to people from outside. Because, every society, through its imperfections, generate a few criminals who can never be categorized based on where they were born. To prove my point, I searched the race-wise statistics of crimes in the USA on the internet and found that the crime ratio tilts towards non-whites. But this data refers to arrests that were made. We should not forget that there can be racial bias involved in these arrests. I have read in newspapers that several studies demonstrating this factor have come out in recent years.
Writers who look at this issue from a sociological perspective have opined that immigration is a more complex phenomenon than meets our primary inferences (Henslin 391). The attitude that the sanctuary cities have to retract this benevolent space given to illegal immigrants is against the spirit of global humanity and will amount to what scholars like Henslin have called as “ a reactive social movement” (p. 415).