Kadampa Precepts 13

"What is the difference between Dharma and non-Dharma?" the teacher Drom was asked by Po-to-wa.
"If something is in opposition to fettering passions, it is Dharma. If it is not, it is not Dharma. 
If it does not accord with worldly people, it is Dharma. If it does accord, it is not Dharma. 
If it accords with the Teachings of Buddha, it is Dharma. If it does not accord, it is not Dharma. 
If good follows, it is Dharma. If bad follows, it is not Dharma." 

The teaching that the Buddha gave to Mahaprajapati Gotami in the Pali Canon as to how she could recognize what really was his teaching, what really was his Dharma. It is very similar to what he said to her. 
Here is Atisa coming from India. He is coming into a new situation, he is coming into a country in which there is very little Buddhism. There was Buddhism before but it has been destroyed as a result of persecution and there is very little Buddhism and even less real Buddhism, pure Buddhism. He is coming into a country into a culture that is not predominantly Buddhist. But he is coming into that situation with his wealth of knowledge and experience and so on and he is relating that directly to the
actual situation in hand. He is giving precepts. Just as the Buddha, 'emerged' into the
contemporary Indian situation with his Enlightenment which was quite incommensurable with anything else that was known at that time and he just taught people out [of] his personal experience. He gave them precepts, which afterwards were collected together in scriptures.
So there is a sort of analogy between the beginnings of Buddhism in India and the
re-beginnings of Buddhism in Tibet at the time of Atisa, as a result of the work of Atisa. No doubt he knew lots and lots of things that he didn't talk about at all. We know, in fact that there were certain things that Drom suggested he did not talk about and did not teach, for instance the Anuttarayoga Tantra teaching with its sexual symbolism and so on. Drom was very strongly of the opinion that this could not but be misunderstood by the Tibetans and he strongly advised Atisa not to teach that, not to make it known. Though Atisa was very well versed in it indeed. So Atisa respected that advice of Drom and did not give that teaching. 
It really means if people are in a very worldly state of mind, a worldly situation the Dharma cannot but appear negative to them. Because it opposes whatever they are and wherever they are at, at the moment. Even the positive things of the Dharma assume a negative aspect, as it were. 
if you are really immersed in, attached to some particular state and the Dharma
says that that state is devoid of any meaning, you can't help but react emotionally negatively. Even though maybe another part of your mind, your intellect may think, "yes this is true." 
Because it's as though you are attracted to something because you take it, or you
experience it as an extension of something which is in you or with you already, but which in fact you ought to be getting beyond. In other words, you take to something because it seems to confirm your existing attitudes, even though those attitudes need to be undermined.