Slippery slope fallacy.

We shouldn't object to a reasonable law just becasue it might, theoretically, pave the way to an unreasonable law.

In fact, this is put in place as an alternative to the kind of law being enacted elsewhere, right now, which is much worse; the ones requiring ID based verification for accessing many online services. This one provides an alternative solution, which is far more privacy preserving, and leaves all of the actual power in the hands of the owner of the computer.