I came to the same conclusion, though perhaps for different reasons. "Zero tolerance policies" have been implemented in public schools and quickly degenerated into stark nonsense: kids suspended for having an aspirin on them, or making a drawing a gun, or giving a girl a peck on the cheek.
I decided that I did not want to volunteer in an atmosphere of suspicion, and would not give up my civil and canon-law rights to the presumption of innocence. It was the right decision: the name of someone in my parish was confused with that of a person who did have a criminal background, and he was suspended for several weeks until the mistake was cleared up. But the interim was hell for him.
Eventually, the diocese decided that choir members are really no different from ordinary congregants, and did not have to go through this stuff if they did not work with children. So I went back to volunteering.
The whole thing's a bit overboard, IMO, rather like the Transportation Security Administration, but no one can justly accuse the Church of inaction on this issue.
The cynical SOBs that set up this "Protecting God's Children" BS have a custom carved millstone waiting for them, if they do not repent.