Because I prefer a value system that's usually not self-contradictory over one that's usually self-contradictory.

Sometimes values you really have are in conflict, you have options to achieve one to a certain extent, or to achieve the other to different extent, and you have to figure out which is more important to you. This does not mean that you give up the value you didn't choose, just that in that particular situation, it was more effective to pursue the other. Policy Debates Should Not Appear One-Sided.