First, your "Take Action" link doesn't work. Second, I don't really care if "NSA's Supercomputers" are scanning my emails, text messages and even my phone calls. They're not really interested in my activities. Third, I'll let you in on a little secret, Its not just overseas communication! If it keeps safe, what do I care!
(1) if you really believe that, then you would have no problem with a group of strangers searching your house, your bank records, safety deposit boxes, all your digital assets, etc. And by "etc" I mean also strip searching your family members or loved ones if "necessary". Did I go too far there? If so why? Because after all, "if you don't have anything to hide, you have nothing to fear". Who gets to decide how far is too far?
(2) And you might respond, "but these aren't strangers searching my stuff and family, these are duly authorized government officials." Well, duly authorized government officials are flawed human beings like all of us, and the ones doing the searching are most likely not elected by anyone.
And also, these people in power at the moment, whose motives you trust, will most definitely not be in power forever. One day, there will be authorities in power whose motives you don't trust at all, maybe for very good reasons. What then?
That's why the erosion of privacy rights is worth fighting.