I think it means that they wouldn't cooperate with him, and with some of his requests. Lloyd being Lloyd, he probably got into a few arguments with them and, unable to just drop it and move on, decided to take a shot at them for not showing him the deference he expects.
Groups like Extinction Rebellion aren't exactly hurting for press coverage due to the nature of their protests. I think Evans thought he could bring Tibor, tell them he was a "filmmaker" and they'd be glad he was on-board. These are people who put themselves in danger by using their bodies to block irate commuters and attach themselves to prominent landmarks. They want participants, not some guy with a camera who would be the first to yell "Press" the minute the police came to haul them away.
He might have already had a few suggestions in mind for them as he had tweeted earlier about having some sort of script ready for the event. So was it going to be pro or con? They had no way of knowing and probably told him if he and Tibor are not there to participate, then they wouldn't be welcome.