As the common wisdom goes: Al Capone was not arrested for being a crime boss but for tax evasion. Why bother setting clear boundaries on what behavior is or isn't anti-revolutionary if you can just make sure everyone already violates the law based on technicalities and then just decide who you want to arrest for it as necessary?
If anything "spy on your neighbor" plays into what I said: you not only need to worry about getting on the bad side of the authority (i.e. those able to enforce the law against you) but of literally anyone else who might have it out for you. The legal basis for arresting people is just legalistic window dressing to create a pretense of law and justice.
This is, by the way, the biggest practical distinction between the authoritarianism of the Soviet Union and Nazi Germany: in peak Nazi Germany the police would just drag you off the street and throw you in a hole or shoot you for treason, in the Soviet Union the police would disappear you into a gulag but only after giving you an unwinnable mock trial where you would be put on record to confess (after torture if necessary or desired) to your treasonous counter-revolutionary beliefs. Because one followed purely from "might makes right" and the other tried to maintain a pretense of ideological principles and justice. Not that this mattered much to those on the receiving end - you'd still end up dead or imprisoned.