If you shoot the first wave the second wave, and successive ones thereafter, don’t happen.
In the end it is the least-harm approach to solving the problem.
Perhaps a more humane approach would be an easier sell. How about a 200 yard wide moat filled with hungry alligators and piranha?
for more than 10 damn years, I have stated on FR we need to place landmines at the border but NOOOOOOOOO max, you are a meanie