I refer to Arbibi Ashoy's letter that suggests discrimination against bumis in the employment market. This is not surprising at all.
Many of the non-bumis have also suffered discrimination at the university-entry level. They have to do two years of STPM, instead of one year of easier matriculation to get into a local universities. This resentment might have been bottled up over the years.
When these unhappy non-bumis are in positions to select employees, they might prefer non- bumis because they are perceived to more competent, having gone through a more rigorous education.