And there will never be a clear dividing line, such things are imaginary contructs of the mind.
For instance, there is no clear dividing line between the earth atmosphere and space, just a constantly thinning amount of air and pressure.
The ISS is undoubtedly in space, yet it encounters wind ressistance.
Similarly no clear delineation exists in rights. Even something as simple as a right to life, or a right to not be killed, has exceptions and caveats and addendum.
If you want to wait til a clear dividing line exists you will wait forever, because those lines are a human creation.
As for the slippery slope, it doesnt have to be unstoppable to be something to watch carefully.
No slippery slope is truly unstoppable, its just that sometimes stopping the slide requires blood be shed, I think we can agree its better not to reach that point, hence we worry about the small things.
I dont consider this instance to be something to be worried about, but I worry that it might train the next generation to accept greater government tracking.
You may look at the slope and say "thats not unstoppable" but its also no reason to jump up and down on boulders, you might be wrong.