When do you say something?

As our great nation struggles to find its way in this turbulent era, she calls on her citizens to work together toward healing old wounds. To that end, a new dialogue must take place. I understand this may be very difficult for some of us, as it may fly in the face of what we thought was a clear demarcation between right and wrong. However, this dialogue starts with a simple question:

If someone has a piece of food or something on their face, When do you say something? 

The debate becomes even more heated when dealing with a stranger. In the following real life illustration I was that stranger. And it wasn't food. It was a massive grease stain acquired from something at Home Depot. Probably from a lawn mower blade. Or from that interesting looking pipe cutting machine in the plumbing section that I felt compelled to screw around with. Anyways (see related post here). I walked through the entire goddamn store with this huge grease stain on my face looking like 'Pig Killer' from 'Mad Max Beyond Thunderdome' and no one had the decency to tell me about it. Please, for the sake of our country, and all that she stands for, if you see someone with toothpaste, mayonnaise, stray bits of makeup, remnants of shaving cream, gravy, ketchup, catsup, cheese, or even grease clinging to their face, do the right thing and tactfully let them know about it. 

The same goes for something stuck in someone's teeth.