He has every right to protect his companies intellectual properties.
As a general rule, that is true for all companies that own intellectual property.
But Microsoft has a long history of making phony claims, so there is ample reason to believe that Ballmer is trying to divert attention away from their pathetic lack of true innovation.
The U.S. Patent Office has rejected some of Microsoft's specious patent claims in the past, such as the FAT file format claim.
Ballmer should be specific about his claims by citing the patent numbers and the packages that he is alleging infringe on Microsoft's rights. So far, he is only spewing a cloud of SCO-like FUD.
Also, Microsoft is obligated to license their intellectual property as a condition of settling their conviction for violating the antitrust laws.