What about the heretic receiving the communion, sash or not?
The big thing about being someone who did wrong is that one does not have to advocate against the Lord’s word regarding something that is not correct. People can have something in their mind, which just cannot be judged. People cannot generally read minds. Evil can exist for some time amongst the good, such as wolves amongst the flock, or tares amongst wheat. But evil breaking away from good is often a process rather than an immediate event. Sashes are probably not the only offense, if one was willing to openly shout in front of the congregation, as much as wearing a particular labelled sash, either way is showing a committment which can simply not be in harmony with what the Lord teaches as correct. Heretics can repent, however, and to some extent, there is a matter between the Lord and man.
Correction: Only the Lord can know the thoughts and intentions of one’s heart.