Jesus knew what Jesus meant when He spoke those words in John 17:21-22. If someone wants to believe that Jesus included islamo-fascists and other cults in that verse, then the onus is on them to prove that.
I don’t think Jesus afterwards winked and said “When I use the word ‘believe’ I want you all to know that ‘fake belief’ is just fine with me.”
Bluntly..are you “one” with Rome”?