Dear Alex Murphy,
"In the last year I haven't found two Catholics who can actually determine whether this or that Protestant baptism-as-sacrament was actually 'valid'."
Folks might be hesitant to try to judge the particulars of a specific set of circumstances. I know I would be. Especially if the circumstances aren't clear-cut, or there are gaps in the information presented.
"I suspect this is because (using your example) you've already denied the validity of virtually all Protestant ministers who would have administered said baptism."
Every year, my parish accepts non-Catholics into full communion with the Church without requiring any sort of baptism, conditional or otherwise. That means that my priest has already decided that the individual's non-Catholic baptism was absolutely valid. If there were any doubt, the priest would perform a conditional baptism.
But that is a priest's job to determine, not mine. I know the general principles, but it really isn't my business to go applying them willy-nilly to folks whose circumstances I know incompletely.
sitetest
Campion: Anyone is a valid minister of baptism.
sitetest: ...any human being may be the valid minister of baptism (at least in the Latin Rite).
Message received. I profess I still don't understand why that's the case for baptism, but not for the Eucharist, but message received. If either of you can explain it, please feel free to.