To fumble is to not date someone you could have because of various reasons. You always come to regret it. You either didn't know they liked you when everyone else did, said something weird in front of them etc..
And it sucks ass.
Person 1 "Man!! Everyone knew she liked you!! All you had to do was ask, how could you fumble this hard?"
Person 2 "I know, I fumbled so hard."
One of the following..
1. One of those cultist alt right people who follow him blindly, a Nazi.
2. One of those people who genuinely enjoy his music and separate the art from the artist.
3. Someone who hasn't heard about the Kanye West controversy and plays his shit.
4. Someone who claims they're not 1. and defends him by saying he has mental issues and didn't mean any of it.
Person 1"Are you a Kanye West Fan?"
Person 2 "No bro wtf"