If I were the rabbi of a shul [which I wouldn't be b/c a] I am no rabbi, b] no shul would want me and c] I wouldn't want such a job], I would not invite a Christian pastor to speak in my shul. A shul is not a place for darshanim who are believers in Avoda Zara.
On the other hand, if a rabbi makes the decision to invite such a person to talk in shul about his support of Israel, that doesn't make him a Rasha.
So if a person uses social media to try to destroy such a rabbi, he is playing with his Olam Haba. He threatens other people with Gehenom but to be מלבין פני חברו ברבים in such a way is "booking a ticket" for his own trip to Gehenom.
Dangerous.
There is no היתר to publicly humiliate someone EVEN if you disagree with them.
I am relating to something that may or may not be going on now.....
