Side A abuses (legal, governmental) power, and instead of "lynching" them for that, we turn the issue into "this will become bad only because of side B will do the same". To me it looks like someone supports side A, and wants to limit the "badness" of whatever they did, but still can't support the thing, so they find the way out by claiming that the other side will do something bad with that data, as if the collecting the data (chats,...) isn't bad enough by itself.

I understand your analogy with friends and facebook, and explaining that stuff to your grandma in this way would probably work... maybe even better if you used "your neighbor Sally works for the government, she could read your chats too, do you really want that?"... but on a technical "forum", it (to me) gives off very politically biased vibes.