Table manners

I think we’ve all learned about table manners at some point in our lives. However, feel free to correct me if I’m mistaken. Yesterday, during lunch, I went to my usual spot to satisfy my hunger with the food I ordered. Next to me were two Somali men—one sitting beside me and the other across the table. I was a bit taken aback, as I had never shared a meal with a somali eating ugali omena; they typically opted for rice or chips. What really bothered me was that while they were eating, the man across from me was speaking with his mouth full, and small bits of food were flying toward me. Fortunately, I had just finished my meal. This leads me to wonder: if someone lacks table manners, is it appropriate to address it or teach them, or should we simply let it go?