From St. Thomas's
Summa III q. 82 a. 9 c., a beautiful syllogism:
1. [H]eretical, schismatical, excommunicate, or even sinful priests, although they have the power to consecrate the Eucharist, yet they do not make a proper use of it; on the contrary, they sin by using it.
2. But whoever communicates with another who is in sin, becomes a sharer in his sin. Hence we read in
John's Second Canonical Epistle (11) that "He that saith unto him, God speed you [
ave], communicateth with his wicked works."
3. Consequently, it is not lawful to receive Communion from them, or to assist at their mass.
Or, more simply:
1. [H]eretical, schismatical, excommunicate, or sinful priests […] [sin in their improper] use of ["the power to consecrate the Eucharist"].
2. But whoever communicates with another who is in sin, becomes a sharer in his sin.
3. Consequently, it is not lawful to receive Communion from them, or to assist at their mass.
Since a priest sins by not stopping Communion in the hand, then it's sinful to attend a church where Communion in the hand occurs.
Thoughts?