I seriously doubt if those that actually turned their backs actually had anything at all to do with an assumed Bloomberg invitation or request.
If any organization I belonged to invited a person I strongly dislike in political terms, I would likely do the same.
It’s a soft way to tell management (in this case the clergy or others in charge of the church) it’s not acceptable and embarrassing them at the same time. Those that made the Bloomberg arrangements should have been aware of such consequences.
Black Lives Matter just took over a Klobuchar rally forcing her to cancel it:
https://twitter.com/WhyItsArbitrary/status/1234291553243406339