It's not about whom I can teach anything or not, it's about who can be taught anything at all. Let me tell you a small incident here. I used to learn Horse Riding while I was in High School. Initially for a couple of times my Trainer/Coach gave me a horse that was docile, and the horse followed my commands 80% of the time, considering I was new to all that too. Another few times he gave me a horse that did exactly opposite of all my commands, I tried to turn him left, he went right, I tried to stop him, and he kept going. One time my trainer gave me a horse which did not move at all. No matter what I did for forty-five minutes, I couldn't move that horse on the ground even an inch. Very frustrated, I climbed down, walked away and I approached my Trainer and asked him, what kind of horse you gave me today, he is not moving at all, he is not doing anything at all. He laughed and said Horse Riding is not only about Riding/Controlling a Horse. Horses are not Cars, for all cars first gear, second gear, neutral, brakes are same, all will behave in similar way, but horses won't. You need to learn how to handle, how to deal with different horses. 

I did not become a professional horse rider, but I learnt a very important lesson of my life that day. So you see, its the same thing. Some people are really serious about their Spiritual Life, their Spiritual Growth and they will make their best efforts to move forward. Some will do the opposite of what is being told to them, I am still fine spending some time with them hoping that someday they will be able to follow exact directions, but there is a limit until when I just leave them alone. But some just want to be in the Spiritual Field, but will NOT move even an inch despite all my efforts, and I am left with no choice but to walk away from such people. And it's not that I feel happy about such situations. I pity them, I feel concerned about them because the opportunity to walk the path of liberation arises ONCE in many lifetimes, and these people have no idea what they are losing, so I feel much love and concern for such people, and I hope for their genuine return.

~ Adiguru