Well, you might be a rancher on the southern border whose property is routinely overrun by drug smugglers armed with AK-47s. Actual examples here.
Surely a man has the right to defend his life, his family, his property, and his livelihood from domestic and international criminals. Having that right, he has the right to appropriate means for conducting that defense. If you disagree then you are morally obtuse. If you say that the Federal government provides adequate control of the border, then you are badly misinformed -- or lying.
Not only do the Feds not control the border adequately, the Obama administration had the chutzpah to sue Arizona over S. B. 1070.
The second rancher to be interviewed in the above linked article tells of an incident when his child was taking a shower. An illegal alien reached through the window and grabbed the kid, who for months thereafter refused to take showers! What really got me, though, was that the rancher referred to the alien as a 'gentleman.'