My college experience was made massively more enlightening because it exposed me to people from very different backgrounds. I grew up in a nearly 100% white suburb of Detroit, and even though I only had to walk 5 blocks north from my house to be in nearly 100% Black Detroit, I had never had a real conversation with a Black person until college, where both dorm life and coursework put me in close frequent contact with many people from diverse backgrounds. My undergrad degrees were in physics and mechanical engineering, and many engineering courses involved group projects where you end up spending maybe 100+ hours with the group members over the course of the semester. This situation specifically lead me to a number of eye-opening conversations and experiences where I discovered my own blind spots. For example, one time when I was driving to Home Depot with a Black electrical engineer groupmate and friend, I was pulled over for no obvious reason. I'm white and my father was an FBI agent so I have always been comfortable around law enforcers, so I asked what the issue was but the officer gave a vague non-answer (I made a "suspicious turn") and asked my friend for his ID. I asked the officer for clarity and why he would need the ID from a passenger if it was a moving violation, to which he asked how I knew the passenger. I explained we were engineers going to pick up supplies for a project, and I could see in his demeanor relax, right before he said "that explains it, something just didn't seem right" and let us go. After heading on, I ignorantly wondered what that was about as there was no legal basis for it, and my friend asked if I seriously didn't see that the cop just thought it was strange and possibly a sign of trouble/distress that me, a bookish white young man was driving with a Black young man. I couldn't see that in the moment, but in retrospect it was obvious. I was able to better see part of the world that was hidden from me because I was with a Black person who I met through school. Without the coursework, I wouldn't have developed that friendship, and without the friendship, I couldn't have started a real conversation about what it was like being Black in America and what other stuff like that happened to him.

That's just one example (one of the most impactful for sure) of the great extracurricular educational value I got out of being around a diverse group of people.

As a high schooler, I held similar views to many of the people commenting on this link, that affirmative action was unjust. Today, I know that my educational experience was greatly improved by my exposure to people with very different lived experiences, educational backgrounds, cultures, and perspectives. My understanding of the world and the problems to be solved is so much richer because of these experiences and connections, and universities absolutely improve the quality of the education by promoting and facilitating these connections. Even excluding the societal benefits of affirmative action (eg helping a systematically oppressed population gain access to better economic opportunities), affirmative action is a smart and good policy for universities to embrace.