> My question is: Why does your online activity deserve special protections that activity offline does not?
You have it backwards. This is far more invasion than anything they ask for offline.
Your social media profiles (particularly private ones) may contain private conversations you have with friends, colleagues, and love interests. To use an offline analogy, it is like the US government asking you to tape record private conversations you have with friends at home, and then give them the recordings to gain access to the US.
Would you support the US Government asking people to tape record private conversations? Then why is it ok when it is on a technological platform? Why is voice more protected than text? Do you feel like people going to Disneyland should give up all privacy to do so?