Widely accepted...hm. We have a source that claims the idea that Boniface had a demon on retainer was widely known:

He has a private demon whose advice he follows in all things. Whence he has said once that if all the men in the world were on one side and he on the other, they could not deceive him, either in law or in deed, which is impossible unless he employs the demonic art. And all this is widely known.

(trans. Charles Wood)

Scholars typically recognize this description as a demonic familiar, like you might know from witchcraft. The idea of a personal demon that stays with someone at all times and give them aid was juuust coalescing in 1303, so some writers have depicted this as a situation of demon veneration or a "pet" instead.

But if you click through and read the rest of the source, you'll see the problem quickly: this is a list of accusations of heresy against Boniface drawn up by William of Plaisans for King Philip IV of France, Boniface's silver screen-friendly Mortal Enemy For All Time. Furthermore, this is actually the second set of charges that Philip got someone to write up against Boniface. The first set, by William of Nogent in spring 1303, revolved around Boniface's illegitimacy as pope and bore a decent resemblance to earlier sets of charges or casual accusations. William of Plaisans' accusations of heresy--some of which are demonstrably true, most of which are utterly wild--were new.

Jeffrey Denton argues that the repetition of "all this is publicly known" "this is widely known" was both a legal formula and a purposeful strategy. Essentially, in a legal system where fama or reputation/gossip/"the grapevine" was valid evidence in court, an accusation or assertion that something was widely known was self-fulfilling prophecy. People hearing about the charges didn't just learn that someone thought Boniface was a sorcerer; they heard that everyone thought Boniface was a sorcerer. And so their testimony could be just that: "it is known," not "I heard."

As to impact on the Church: it certainly had an impact on the credibility of Boniface. Dude is on the brink of being placed in hell by Dante in Inferno! However, we are still in the days where furor over the person of an individual pope does not refract onto "the papacy" as an office, and certainly not on the Church as a whole. It's true that the reason for the accusations in the first place is a major Church-secular imbroglio over whether the pope or the (French, in this case) king outranks the other. But this doesn't really have anything to do with whether the Church is valid, Christianity is valid, the pope is the rightful head of Christendom, etc.