Asking for Evidence Is Not Skepticism
A hardcore skeptic, one that David Hume would call an "excessive," or (unmitigated) Pyrrhonian , skeptic, would not ask, "How do you know P is true?" Rather he would ask, "Why should I believe anything put forth as evidence for P?" The first question acknowledges the possibility of knowledge and hence is not the question of a philosophical skeptic. The second denies or at least seriously doubts that any knowledge is possible. That is skepticism (in all its self-contradictory glory).