If software development is inventing, why aren't software patents OK?

I'm in part playing devil's advocate because I don't agree with software patents. But the problem with us (technical people) not communicating consistently is that if we can't get our story straight how do we expect others to understand what we say?

In the software patent arguments we stay firmly away from the word invention, wary of how it will be used against us. Yet here, for the sake of arguing about estimatation, we seek to embrace the word invention?

I'm not sure we can have it both ways. We've got to collectively get our story straight.