The argument goes that Our Lord let Judas eat at the Last Supper, so who is anyone to withold communion from anyone? (Particularly a politician openly co-habiting and a well-known record of support for abortion.)
It is well established in moral and canonical literature that a minister cannot withhold holy Communion from an occult sinner, even where the minister knows of the sin and knows of the impenitence. Citations [added: Abbo-Hannan II: 854-856; Dom Augustine IV: 232; Davis III: 206-207, etc.]. That’s why Canon 915 operates only in the face of manifest grave sin, not simply personal sin.
In fact, as important as the prevention of sacrilege is in the operation of Canon 915, it is not the only basis for the canon; rather, the prevention of scandal is also a key consideration, but scandal arises only from public behavior seriously at odds with Church teaching and order. Judas was an occult sinner, and Jesus did not expose his inexpressibly grievous, but to that point still private, sin to public view by withholding Communion from him.