I guess you really aren't as smart as I thought you were. It's not that I don't have a valid argument; it's that you apparently don't understand it. Logically, there is no comparison between illegally crossing the border and killing someone in a fit of rage, and then claiming you are justified.
For one thing, those illegally crossing the border don't claim they have a moral right to do so. They know they are breaking the law. Also, if we follow your reasoning, everyone who skirts or breaks the law, any law no matter how inconsequential, is equal to a vigilante who murders someone because they believe they have a moral right to do so. The actions are not equal. Trespassing and execution are not equivalent. That is why the legal system has different punishments for different crimes.