An important thing to note is that for the executives in question, this is a compliance and PR issue, NOT an ethical issue!

These laws don't exist in the USA and from the perspective of the executives (and the wider American public) there's nothing wrong with paying permanent and temporary staff different wages. The actual monetary amounts are also pretty small (up to 100 million liability) which Google can easily afford, they just really didn't want to have to try and figure out department budget adjustments.