That's Biruwa's decision. He needs to figure out whether he wants to let it pass or confront it. There are pros and cons either way. Speaking up about this kind of incident - or any other form of harassment, bullying or threat - is usually better for you emotionally. There are so many factors involved in something like this, that what works for one person in one situation may not work for another. To each their own. Whatever he does, hope he finds his peace and moves on.