The thing people don’t understand is that disciplines are not immutable. If they were immutable, we would never change a thing. There wouldn’t have been a Tridentine Mass to begin with. As the Catholic Encyclopedia shows (I would quote but New Advent seems to be down this morning

), this would be burdensome to the Faith. The simple fact that is often overlooked is that all disciplines are not proper for all times which is why we have change in the Church.
While the disciplines in an of themselves cannot bring souls to impiety (Stmaria this is pre-Vatican II teaching which has been quoted from many sources so I find it hard that you can disagree with that) society can change and the discipline might no longer be prudent. That is not the fault of the discipline.
So why was Pope Paul so worried that communion in the hand might be “dangerous” for the faithful. If a discipline in and of itself cannot lead to impiety why worry?
Pope Paul had Father Bugnini send a letter to those Bishops where he had allowed an indult for communion in the hand.
“His Holiness thinks the Bishops should be reminded of their responsibility…and also to control the indiscriminate spread of this practice, which in itself is not contrary to doctrine
but is nonetheless debatable and dangerous…”-
Reform of the Liturgy by Annibale Bugnini How can a discipline approved by the Pope be “debatable and dangerous?”
Because of protests from conservative bishops Pope Paul ordered Father Bugnini to “temporarily suspend the publication and implementation of the indult”
It was decided that a letter would be sent out to all the presidents of episcopal conferences asking for their (name removed by moderator)ut on communion in the hand.
Part of the letter says, “this difficult situation calls for serious reflection…it is necessary to anticipate what the effects of such a **change of discipline **will be: a] on priests and ministers of communion , b] on the faithful, [c] on the way in which the bread is made [it will have to be denser in order to prevent its slipping from the hand as easily and also to prevent as far as possible, the breaking off of fragments] [d] on material changes in the churches the possible removal of communion rails}"
Why was Pope Paul worried that this “change in discipline” might cause problems if discipline in and of itself is infallible and cannot lead to impiety?