Letter of the law

Well, I am in Columbia SC. I spent three days here on a job site. The airport is beautiful and staffed with zealous TAS agents. After traveling through Denver, Pasco, Portland, Pittsburgh, Philly, DC Reagan, this one made me toss some of my over the counter meds. The losses include my contact lens saline (it was a 4 ounces bottle but partly used) my Pepto Bismol (factory sealed and 6 ounces) but they let me keep my 1/3 full Pepto because it wasn't over 3 ounces. It was the same size container but it wasn't full. FREAKS. So why did I have to toss my Unused Pepto and partly used saline but I was able to keep my partly used Pepto? These are the in-consistencies that really suck the life out of traveling.