These are the main reasons.
1. Joe Lacob, the owner said his team is "light years" ahead of the rest of the league. Then went on to blow a 3-1 lead to the Cavaliers in the NBA Finals a few months later.
2. The Warriors organization and fans suggested they lost that series only because of Draymond Green's suspension in game 5. Yet, they had two more games after that game 5.
3. If Draymond Greem suspended for 1 game is the only reason your team lost, why not run it back to prove that is the case? Instead they pursued a top 3 player Kevin Durant. Cowardice.
4. Kevin Durant at OKC nearly beat the Warriors, they also blew a 3-1 lead. He could've tried to run it back to beat the Warriors. Instead he took the easy way out and joined the team that beat his. Cowardice.