I wouldn't call them athletes since I think an athlete is someone whose sport is defined with physical exhausting activities and not the mind, fast reaction in the fingers or stuff like that. So, for me people like darts players, pro gamers, chess players or people who participate at Olympic shooting aren't really athletes to me but that doesn't mean that they don't deserve the same respect if they invest the same time to be one of the best.
I mean, even gamers often say that pro gamers don't deserve respect since they do nothing as playing videogames but that is as true as saying that the best football player on this planet is doing only what million other people do as well, playing football...
Playing Starcraft or football for fun or to train to be one of the best in football or Starcraft is something totally different. If it would be so easy many more people would be so good in these games but they aren't because you have to learn every possible strategy, learn what to do in every single second sor like in fighting games, train to be the guy who has the advantage of one single frame or pixel. Why do most people (also gamers who play as much as pro gamers) not do it? Because it is super stressful and not really fun. You have to have the desire to do it as much as athletes have to have it to invest hours every day to get better and not to have fun.