I don't think Posner is disagreeing with the law, although he may be interpreting it in a somewhat unusual way. He gave detailed reasons why he threw out the case, mostly (AIUI) that neither side had adequately estimated the financial damage caused by the other company's infringement and that asking for a competitor's product to be outright banned was too harsh a penalty. This does seem to be in contrast with the Oracle-Google lawsuit, where there was a full trial to determine infringement and then afterwards they worried about the damages.
In Oracle-Google, there was plenty of pre-trial work on damages. IIRC, Oracle had to do three rounds of damages reports before the trial (the second and third because the previous reports were not satisfactory). Post-trial they would have determined what the damages actually were, but, in order to get their trial, Oracle did have to make a showing that there were damages worth trying.
Oracle had it easier because there were willing to license the patents and copyrights at issue (and Sun had even talked to Google about this). That made the lost licensing revenue a helpful data point with respect to damages, but with or without that there was a hurdle Oracle dealt with that Apple/Motorola didn't (based on Judge Posner's ruling).