Understanding your opponent is vital, misunderstanding your opponent is detrimental to success. Information inaccurately sourced or evaluated can lead to great struggle and strife; can lead to confusion and defeat. Avoid quick assessment or popular belief, dig deeper and be prepared to admire your opponent even as you prepare to defeat them.
Pithy Ponderings 
Wow, I just read Sun Tzu!
“If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.”
Tzu, Sun. The Art of War. Edited by Dallas Galvin. Translated by Lionel Giles. Reprinted ed. New York, NY: Barnes & Noble Classics, 2003.