Me'ila 5: Cleaning Clothing that is Holy because it was Touched by Sanctified Blood

Today's daf is based on verse 6:20-21 of Vayikra: when discussing a korban chatat, a sin offering, "Whatever touches its flesh will be holy, and if any of its blood is sprinkled on a garment, you will wash it in a holy place.  But the earthen vessel where it is cooked will be broken, and if it is cooked in a brazen vessel, it will be scoured and rinsed in water."

We learn that sacrificial blood is to be treated as holy.  The laws pertaining to the sacrifice will be transferred to whatever its blood touches unless it is cleaned properly.  We learn that clothing had to be washed in the Temple courtyard and metal vessels could be heated until the blood was gone, but earthenware vessels soak up the blood and so they must be destroyed.  

Today's Gemara quoted a Mishna that limits this law: it only applies to blood that can be sprinkled on the altar.  If the korban was disqualified for some reason (if the sacrifice was disqualified at some point, if the meat was left past its appointed time, if it left the courtyard, etc.), its accidentally spilled blood did not need to be cleaned.  Sacrifices were never good if they were slaughtered in the wrong place or time, or if the blood was collected by someone forbidden to participate in the sacrificial service.  This blood need not be cleaned, either.

It is fascinating to try to understand what is permitted and what is forbidden when it comes to something as sacred as blood.  How could it be that some blood is holy and some blood is not?  I am inspired to read something more specifically focused on rabbinical understandings of blood and sanctity (with particular interest in menstrual blood).