First – correction – s/b more than the host’s treatment of him.
Second – Logician and Cheftza, it is a very delicate issue. If you look at our history, reasonable people felt it was OK to “call out” a godol if they had a reason to think he was in error.
Think about this – R’ Moshe Galant, R’Moshe Zacuto, and R’ Chayim Benveniste all initially followed Shabtai Tzvi. They were wrong, and it was clear to laymen and other rabonim why.
There were a number of gedolim 2 and 3 generations after the Besht ( my g x 7 grandfather and his brother among them) who had great challenges from their communities of Frankfurt and Nikolsburg because of their affinity for chasidus. Not every individual in both those communities was a chutzpan denigrating them – some had legitimate questions and concerns.
In our time – R’Moshe Feinstein famously gave a psak allowing women to wear cullotes and pants made for women, but then had to retract it under much pressure. There were many non-gedolim who called for the psak to be reversed. I don’t hear anyone condemning them.
Obviously there is an issue of kovod, and obviously if there is a reason to disagree, it needs evidence, halachic support, and even better the haskomoh of a different posek. And obviously it has to be done in the most gentle and respectful way. But we aren’t catholics, who have a pope who they consider infallible. That is the road to making a man into a god, and that’s not yiddishkeit.