Strictly speaking, it wasn't Serrano who sought controversy. The photo was exhibited in the 1980s with no adverse comment until the moral majority decided to make it a scandal, particularly the Replublican senator who tore up a copy of the photo.
He has said that he used bodily fluids (initially blood and milk) partly for their purity of colour but also because of the Catholic emphasis on body fluids, e.g. blood of Christ.
I could really care less what the moral majority did or didn't do. This entire issue was not created by the moral majority. They may have jumped on the bandwagon later because of some politicians desire for more publicity, but for me that is unimportant. You will never convince me that Mr. Serrano was not attempting to create controversy. Whether or not it created any public controversy when it was first exhibited, I do not believe for one moment that Mr. Serrano could not have known that it was controversial from the very beginning.
Had he not specifically publicized the materials he used then there would have been no controversy. Religious art of all types can be found everywhere and we will likely never know what was used in its creation. For all we know Michangelo used a bit of urine to mix his colors on the Sistine Chapel. I seriously doubt that he climbed down off that scaffolding every time he needed to relieve himself. Whether or not he did, he did not feel it necessary to advertise his choice of materials.
Finally, the idea that the only way he could get his colors mixed right was to use his own blood is pure, unadulterated BS, and everyone knows it. There are thousands of ways to mix different colored pigments to come up with hundreds of thousands of different colors. Just go down to any paint store if you don't think it is possible.
I stand by my original assessment. Mr. Serrano's art is entirely dependent of controversy, not on any artistic merit. It is totally up to him if he wants to piss off the pope. But that doesn't make his work art.