"Even the good person attains birth in the Pure Land, how much more so the evil person."

I think I understand the reasoning here-- if practice isn't effective, then the evil person, who doesn't practice or I suppose, do anything good, isn't planning on getting to the Pure Land by his own means, he's going to have to rely on someone else to get him there.

So, after this, if one's goal is to get to the pure land, what is the rationalization for ethical behavior?

(Let me emphasize I'm not trying to imply a suitable reason for being ethical isn't there, I just haven't gone in depth far enough into Shin Buddhism to know what the answer is, and I find it bemusing)