no mesorah:
You need a mesorah, or else you have nothing.
To be brief, two points will suffice:
1) His position gives him zero permission to violate halacha and enter a church sanctuary, all the more so during a religious ceremony.
2) It is not at all “hard to pin down exactly why we do not go into churches”. It’s rather simple, as you can see from contemporary poskim and going all the way back.