It encourages more illegal aliens to come to this country and encourages more of them to continue to ignore other laws. When they come here illegally, they come without the benefit of explanation of and responsibility for our laws. Most of these people come from countries where laws are selectively enforced if at all, and contempt for law and police is common. When they come here without the benefit of supervision from ICE, they bring their attitudes with them. When a U.S. citizen marries an illegal and encourages MORE of them to come to this country illegally in hopes of finding THEIR free pass, it just encourages more of them to break our laws. The statistics are tragic. Innocent people are victimized by the illegals who either deliberately violate our laws or just believe that laws don't matter.
Really, illegals are responsible for a statistically significant number of fatalities and injuries in DUI collisions, roberies, gang related crimes, drug related crimes and other violent crimes. But it isn't politically correct to discuss that fact.