Applying to a PhD in Machine Learning without much knowledge of the subject
Florian is completely right - the level of knowledge of the field typically expected from new PhD students varies a lot. In many places in Europe, for instance, a Master's degree is a formal requirement for starting a PhD, and the first year is most definitely not there for gaining fundamental knowledge about the field. You are supposed to have a solid working knowledge of the field from the start.


  "I was willing to learn more, enroll into courses and being self taught for the research that they were making"


There is also the other problem with this statement that it is (sorry) incredibly bland and generic. Of course you are supposed to learn more about your field and do related courses. If that is the best you can say about how you are going to get up to speed in the field, I can understand that the professor you were talking to was not exactly blown away by your zeal.