I'm not stubborn, I do adapt to team needs, if I feel like it. But sometimes I feel like freezing people with a Mei, even though we lack support or tank. And sometimes I feel like practicing Genji, or Hanzo or Tracer, even if said characters don't fit into team composition in that moment. That's why I feel like others have just as much rights to do whatever they want, as I have.
Just keep in mind that things are most likely going to change, once the competitive gamemode will be deployed. Until then, maybe stop thinking of your team mates as "mentally retarded donkeys".