Pasta dishes are a staple in many family's pantries and are often accompanied with grandma's favorite spaghetti recipe. When these recipes were created, the modern world didn't have the many concerns about microbes that we do today. Nor were there concerns about seat belts, kids playing in the streets, or, in my family's case: shoes. In a land where helicopter moms are real and Purell has become part of the "back to school" list, it's no wonder that rinsing pasta, in the hopes to eliminate unseemly bacteria, has become a trend. Unfortunately, the only thing that you're eliminating is pasta goodness.
Bacteria cannot survive in a temperature of 120 F or above. Water begins to boil at 212 F. Therefore, once you dump the box of fettuccine, penne, or macaroni into the rolling bubbles, bacteria immediately begin to die. As most pasta's instruct, you cook the noodles for an average of 8-10 minutes. The longer they sit and absorb that scalding water, the more sterilized the pasta becomes. Ergo, there is no health risk to dumping the hot water and al dente noodles into the colander then eating them.
By rinsing pasta after it is cooked, you rinse off the starches which are needed to make the sauce stick to the noodles. Starches are basically a type of glucose and expand through the absorption of water. Think about how sticky simple syrup is. Even though it has a higher concentration of sugar than pasta, the same sugary substance is what makes pasta sauce adhere to the noodles.
So if you rinse your pasta after cooking, you might as well rinse grandma's secret sauce, the jeweled crown, down the drain too. It won't matter how much Merlot you consume, your spaghetti will be a bowl of limp, watery, pinkish noodles and I'm pretty sure that's not how grandma served it.