The cricketer Basil D'Oliveira, whose inclusion in the England team ultimately led to the sporting boycott of Apartheid South Africa, has died aged 80.
I don't follow cricket but the behaviour of the South Africans at the time does demonstrate why that country was boycotted when other regimes that were even nastier have not been.
When D'Oliveira was added to the England team due to tour South Africa the host nation cancelled the tour. In other words they would only participate in sporting contests if their opponents agreed to implement apartheid on themselves. Unlike the USSR, Nazi Germany & China in the Olympic Games (or Zimbabwe and Pakistan in cricket) for example, they forced opposing teams to collaborate with their ideology.