What stuck with me is Lee Sedol's strong emotional reaction, leading him to leave professional Go playing.
It's understandable he didn't expect AlphaGo to be that strong. Or that (for him) losing to a machine took the 'soul' out of the game.
But come on... I've been cornered by Pac-Man ghosts many times. That doesn't make Pac-Man less fun to play.
Nor does losing to the crude 'AI' steering those ghosts. Instead, you play, aim for a high score, see how long you can survive, how many levels you can complete, or how many fruits & ghosts you can eat in a game.
And (if you care) compare how those 'metrics' stack up against other players.
If a machine with superhuman Go-playing ability isn't fun or challenging, then stick to human opponents.
Of course it's his views and choices, and I respect that. But other than providing extremely challenging opponent, I don't see how human-beating machine would take the fun out of a game. Rather the opposite: new tactics, new insights, a raised upper bound for a Go player's strength (human or otherwise), etc.
Some people connect their ego tightly to their accomplishments. Others are emotionally fragile to what they perceive as negative experiences. Some achieve great things by what they perceive as great sacrifices, and have a lot of difficulty maintaining what they have achieved. Some at or near the top of a field perceive their accomplishment primarily as being "best", and are consumed with angst when they are no longer best. The public explanation they give may not describe how they are different than someone trying to understand.
Open up how you frame personality types and life experiences, and you can think of possibilities beyond "I don't see how".
Truly a must watch! (just look at the video comments to be convinced)