Oh Alec has reasons, reasons that can be revealed either by 1. seeing his memory of getting incredible, top notch advice on future conduct or 2. honestly just asking 'what the fuck are you doing' at the scene of his upcoming crimes.

Actually he might be able to get the confession more than some other people might - it's a gnarly scene, but reviewing it I can cut it off before the eye trauma and retain the critical part for my purposes. The major gist of it is Alec being assured by the ethical compass of his little villain group that using his powers for new and exciting types of crime is a reasonable call.