I think that the argument for why software patents are dangerous is the $4.5 billion figure. If companies are shitting their pants to this extent then clearly the patents have a huge impact on business from their perspective.
I have to agree with the parent comment.
Without going too deep into a philosophical discussion, I think that the competitive nature of our society is hindering progress more than anything else. When people learn to build social structures based on cooperation (I consider a small group of people cooperating to compete against everyone else to be too small in scope), we will see progress increase by orders of magnitude. Just look at the advantage the limited type of cooperation we have now has given us over animals which do not cooperate at all. Now scale that up to the next level (open source is a live example of this, in fact). In concrete terms, imagine if, just as individuals in a company cooperate, companies cooperated with each other. Everyone would be better off. At it's root, this is the difference between seeing life as a non-zero-sum game as opposed to a zero-sum one.
So... it's exactly what MS, Apple, RIM, etc. did. They cooperated, combined their resources, and outbid Google for the pool. There's no indication that these patents aren't going to be used. Since RIM is in the group, it seems that the hardware patents are definitely going to be used, and who knows what Apple and MS want from the pot.
I still don't see how this is an argument specifically against software patents.