Don't know that you have cause to sue, but I have been wrong before. The update is not mandatory.
A little different from MS's nonsense, IIRC.
I think you're definitely right in this case. With Microsoft it was more a matter of IE being a first-party application, with the claim that Microsoft's including it by default blocked out competitors, creating a monopoly. In this case Sprint is just pushing applications for whoever is willing to pay them.