First, There is a nice counter argument in the article -

    But what about the argument that the U.S. is shedding crocodile tears? 
    America (and Israel) were almost certainly behind the most successful known 
    cyber attack to date: the Stuxnet virus that impeded Iran's uranium-
    enrichment program. There might be some comfort in knowing that the U.S. is 
    doing unto China what China is doing unto the U.S.

Second, I think people who are saying - "I don't care" to China reading their email account are unaware of the implicit repercussions. Another snip from the article

    "If I had access to your bank account, would you worry? If I had access to 
    your home security system, would you worry? If I have access to the pipes 
    coming into your house? Not just your security system but your gas, your 
    electric—and you're the Pentagon? Maybe nobody's been killed yet, but I 
    don't want you having the ability to hold me hostage. I don't want that. I 
    don't want you to be able to blackmail me at any point in time that you 
    want." 

It's the potential ability for a foreign host to keep you hostage which is the real worry was a citizen.