No, athletes should not have a tougher skin. One of the problems with this world is that people are too tough and have lost their sensitivity. Sensitivity leads to compassion, which leads to fewer crimes and societal issues. There is nothing wrong with an athlete crying for being booed by a crowd.
It must be hard to spend your entire life working as an athlete, just to have the audience boo so loud that you can't concentrate. The audience should learn to be better sports, not just to try to intimidate the athletes that they don't want to win. The athlete was under enough pressure as it was.
The crowd was horrible and showed poor judgement for booing Renaud Lavillenie. This is only one thing in a series of incidents that shows how poorly the Olympic Games have been handled this year. Booing anyone is incredibly rude and uncalled for, and should never be done at a sporting event.
No, athletes like Renaud Lavillenie should not have a tougher skin. The Olympics are an emotionally-charged time for athletes and fans alike. An athlete is first chosen to represent their country at the Olympics, and incredible honor, and responsibility, as well as a recognition of their great abilities. Then, they compete and either succeed as one of the best in the world, or fail to great disappointment. Tears would be a reasonable reaction, regardless of the crowd. The IOC President was right to condemn the behavior, and the athlete was right to be emotional.