I suspect the legal theory goes like this:
By calling our fine, outstanding product "shitware," you have defamed us.
Or, possibly, "You encourage others to engage is practices that harm our business, which somehow constitutes some kind of fraud or conspiracy or something."
Mind you, I agree these people should be publicly whipped for being assholes, but it isn't at all difficult to come up with an internally consistent legal theory to support their claim.
Fortunately, the court saw fit to spank them for being retards.