> Corporations do far worse things to people and to society than sue other corporations for IP infringement.
This isn't just unethical in a general sense. If it were, then yes, corporations do much worse.
The bigger issue is that Yahoo's move here threatens the entire software industry and specifically the internet. Yes, we already have massive patent battles in the mobile space. But they are fought over the selling of smartphones and tablets - hardware. Many of the relevant patents are software ones, so the distinction is not absolute, but at least they still happen in a clearly hardware-orientated space. The players all sell hardware and are already familiar with the patent game from hardware patents. It's bad there, don't get me wrong, but it is - for now - a controlled bad.
Whereas Yahoo's move here does not involve hardware. It doesn't even involve shipping any product at all or even selling one. It's a lawsuit over a website that is free for people to use - one of the most important forms of online business.
Imagine if patent warfare broke out on in the web space. It would be a massacre for big companies and startups alike. Everyone violates patents all the time, its impossible to avoid doing so. If such lawsuits are brought, they would devastate silicon valley. Yahoo's lawsuit here looks, worryingly, like it might be the first attack in such a war.
That's why people are so shocked and react so strongly - and rightly so. Pressuring companies that use software patents, and pressuring their employees to try to effect change internally or consider jumping ship, is something that makes sense for the software industry to do. To do otherwise would be suicidal. Only Intellectual Ventures and other patent holders win if patent warfare becomes commonplace on the internet.