Some quotes from Wallace about the distinction of present/aorist imperatives (pages 716-18)
[the traditional view suggests that] the aorist in prohibitions meant do not start, while the present in prohibitions meant stop doing.
[McKay’s suggestion is that] the essential difference between the aorist and the imperfective is that the former urges an activity as whole action and the latter urges it as ongoing process.
[Wallace summarises] the basic force of the aorist in commands/prohibitions is that it views the action as a whole, while the basic force of the present in commands/prohibitions is that it views the action as ongoing process. This basic meaning may, of course, be shaped in a given context to fit, say, an ingressive idea for the aorist. Thus if the conditions are right, the aorist prohibition may well have the force of “Do not start.” This is an affected meaning or specific usage. But to call this the essential idea is not correct.