How could Yitzchak, our righteous patriarch, have a son whose very nature even in the womb was inclined towards idol worship? [see Rashi - Toldos 25:22]
G-d can either make a person's disposition naturally good or naturally bad. But, even if a person has a natural inclination to evil, that does not mean that he is evil per se, for he is given free choice. Rather, the reason why he was given such an inclination was to rise to the challenge and overcome it. Thus Eisav was given a natural tendency to evil so that he could excel in the Divine service of "quashing" the evil inclination.
Even though he failed in his task, we can nevertheless learn from Eisav that if a person has strong desires to do something bad, it means that he has been given the special Divine mission of overcoming his inclinations.
Based on Likutei Sichos Lubavitcher Rebbe