Nice duck and weave on the "I'm not suggestiong that criminality is a bigger part of mexican culture".
Bullshit, of course you are. And the circular definition of all undocumenteds as criminal because they are undocumented is silly and you well know it.
Similarly your arguement about the "true rates of criminality" are bogus too. Unless you believe that Law Enforcement Officers look the other way WRT crimes involving meztiso three times as often as they do with US Citizens (btw how does a LEO tell the difference between a US Citizen meztiso and a non-citizen?) Are there unindicted, undetected crimes? Sure. But for your argument to have any legs, you would have to make the claim that undocumented residents are better than the average US Citizen criminal in hiding their criminality. And that just doesn't hold any logical water at all.
So that leaves you with police corruption in Mexico based on domestic news reports. IOW you don't know the actual stats. You don't know the actual data, and you don't know the other factors involved. But from this you conclude things about "mexican culture". And that's not bigotted,... uhuh..