I would like to talk to you about this, and I'm also a bit hesitant to do it in this DIR location -- out of respect for forum rules. I'm thinking it may be best to move the thread.
How does Catholicism fit into the situation? Typically civility IMO is more of a matter of etiquette, rather than a theological or religious practice type of matter.
Are you Catholic? Or, is this event you were referring to a Catholic event?
I don't see civility as requiring that someone accept something one believes to be wrong, whether in terms of being inaccurate, or even in terms of being harmful or hateful. To me civility is more like not jumping down someone's throat when you think they are wrong.
To me it is more like treating other person with respect, even if one sees that person to be in error -- not necessarily holding the belief to be equally true as all other beliefs. As far as I can remember from Catholic school following one's conscience meant following what one really understood to be accurate and right. One needs to use one's own brain in the process of doing that, IMO.
In the situation that you described so far, I would say there is a civil response, and one that is not.
IMO, a civil response allows for disagreement between people, without personal attack on the other person.