A "debatable point" is simply one that for which serious/legitimate debate is possible. While it is easy to say that anything could be argued, including the terms "serious" and/or "legitimate" narrow the field considerably. This limits the possible points (or topics) to those for which reasonable claims can be made. For example, imagine that someone has committed a crime. That person is guilty, and even admits it—but it is a first time offense by someone in a desperate situation, such as a single parent stealing a loaf of bread to feed hungry children. One could argue that all crime should be treated the same—a code of strict justice—or one could argue for mercy due to character and circumstance—a code of mercy. The fact that there are two or more sides, supported by facts, makes the point debatable.
If you're looking for one in 1984, I'd have to go with the relative judgment of Winston's actions in Room 101. Was there something else he could/should have done—or was this all that was possible?