The first time I heard about carbolic acid was in "A Tree Grows in Brooklyn" where (IIRC) it was used for cleaning. It seems to be some strong stuff.
Maybe I miss the point of the original accusation, but purchasing carbolic acid does not seem to me to be necessarily "wrong" in any way. And the fact that Padre Pio died with no scars on his hands seems to argue strongly against a lifetime of carbolic acid abuse.
I just think the whole thing is a weak attempt at character assassination.
If he wanted to make his hands bleed, it would seem that scratching his own flesh with his own nails would be much more effective. It seems his use for Phenol was quite ordinary; at the time it *was*, in fact, regularly used as an antiseptic. As an agent to secretly induce puncture-like wounds, it seems a very strange choice.