This is a work in progress
When you encounter Craig, you may notice he is on edge as he is in hiding from Tarantian authorities due to murder charges. If you meet him by chance without the requirements for Backstab Master training, he will tell you to leave. However, being qualified and asking him about training will give you the required dialogue options.
NOTE: Once you have been trained, his paranoia sets in and he attempts to kill you, so beware.