Eklavya and Arjun
   

Arjun was a consummate perfectionist.  He was so keen to learn archery, he practiced his archery even at night and spent hours honing his skills.  When he found Eklavya had additional skills, Arjun came to his teacher to master those unlearned skills.  At no point in the Mahabharat did he ask for Eklavya's thumb or to have him punished for being better.  Arjun simply wanted to learn more skills so he could be better.  Guru Drona feared that Eklavya might surpass Arjun in archery and so demanded Eklavya's thumb so as to make it impossible for him to surpass Arjun's skills.

Guru Drona asked Eklavya for his thumb for a number of reasons.  Read the three main ones on

http://www.pushti-marg.net/bhagwat/Mahabharata/eklavya.htm

All characters in the Mahabharata are very human and are full of normal human flaws.  It shows us each and every person as they are.  If we find ourselves reflected in any of these characters of situations, we need to introspect and consider the consequences of our actions.

Just as no one needs to be told that India and Pakistan are adversaries, no one in the time of the Mahabharata would need to be told that Arya and Un-Arya were political, military and cultural adversaries.  Even under ordinary political situations, neighbouring countries are often considered to be adversaries and the Bhil, Nishad and other tribal communities were restless neighbours of the Kurus.  Genocide of Khandav-vana proves how strong the feelings ran between these different communities.  Taking this into account, there was no need for Shri Vyasa to state the obvious as to WHY Arjun was upset about Eklavya being a better archer than himself.

Arjun behaved as any teeager would have - he was glad that his competitor was taken out of the game.  It took several life lessons for him to learn that it is always better to hone your skill than have your opposition removed by other means.  We all learn in life as we grow up.  What sets Arjun apart it that he does learn and he continues to learn all the way to the eve of the great battle.  Unlike other warriors in the epic, Arjun continues learning new skills.  In fact, he learns from celestial as well as earthly gurus even during the 12 years exile and is the recipient of Shri Maad Bhagvad Gita on the battlefield of Kurushetra.