Well, I might facilitate the theft of my car by leaving the key on the seat, but that doesn't relieve the egregiousness of the act nor the criminality of the perp.
Not all people found guilty of identical crimes receive the same sentence.
But they do get a sentence. The only available option for the courts is deportation. What other sanctions? Jail? Pillory? Loss of voting fanchise and welfare privileges, when they have a natural right to neither? 