Of course, then nobody "leaves us alone" on these things, but we agree by majority on first principles and then argue from those to collectively decide what is allowed and what isn't (i.e. allowed from the people and allowed from the government). Free speech and privacy are examples of such principles. So you can definitely have a social contract where mass surveillance is unacceptable, but rules on not hunting endangered species or owning certain type of weapons can exist[1]. I don't think May should be prevented from arguing for surveillance, but by the same token, people also have a right to oppose her on it.
Yes, this opens us to the possibility of losing the debate on encryption, at particular times and historical periods. Whereas having the iron clad rule that all can do as they please does not. But the later rule, applied in extremis, makes civilization impossible. Because again, we do want to ban people from doing certain things, that is what civilization means. The point that we need to argue is that banning people from having privacy causes more harm to what makes us human than a few horrific crimes do.
The anarchist posture is... complex. But the (absolute) libertarian posture is hypocritical. It wants a very particular set of rules to apply and be enforced by the state (e.g. private property), whereas decrying rules and state enforcement in general.
[1] And U.S. gun-owning folks agree on having rules against owning some kinds of weapons, I would think. At the very least I have never heard one argue for their god given right to own an ICBM on 2nd amendment grounds... is just that we disagree on the type of weapons that should be controlled.