self-satisfied
adj
(derog贬) too pleased with oneself and one's own achievements; smug 沾沾自喜的; 自鸣得意的
a self-satisfied person, attitude, grin 得意忘形的人、 态度、 傻笑.
Even if one didn't know from concrete examples (the 1936 Olympic Games, for instance) that international sporting contests lead to orgies of hatred, one could deduce if from general principles.