If desire is your motivation for practice, then desire will be the result of your practice. If you practice with hate in your mind, then in the end you will achieve exactly what motivated you. It is important that your motivations be sincere and pure. If you practice with sexual desire as your motivation, then you will succeed in becoming a powerfully sexual being. You may be able to have sex with many partners and never grow tired. In fact, the more sex you have, the healthier you will seem. Similarly, a person who practices with hate as his motivating force would not need a gun or knife to kill. He would be able to use his mind power to kill, even if his victim lived several thousand miles away. Motivation in your practice is important. Think clearly. What are your motivations? Why do you practice?
If the motivation is impure, then the mind will remain impure. A practitioner with an impure mind cannot attain thorough enlightenment, see his self-nature, or even enter deep levels of samadhi. Naturally, his conduct will not be exemplary.
Many practitioners claim to be Buddhists, but in fact they have strayed far from Buddhadharma. There are a few masters whose behavior seems questionable. If it is true, then they are not genuine Ch'an masters. However, you should not blame the masters for your problems. Look to yourselves. It is you who do not have deep karmic affinity with Buddhadharma. When you have deeper karmic affinity, you will meet better masters, and you will eventually recognize your reflection in the mind mirror. Of course, if you feel you have karmic affinity with the Buddha, then you have already recognized something in the mirror, and you are probably here on this retreat for the right reasons.