My FI's stepfather is extremely anti-Catholic. To the point he insults me how much he looks down on the religion I was raised into. My FI has decided to join RCIA so that we can share the faith together, and also so we can have a full mass for our ceremony, which has always been important to me. I am worried, though, that his stepfather's opinions will be announced at some point leading up to or during our wedding, and in front of a member of my family. Worst of all would be him saying something in front of my parents. He is a very opinionated man and does not censor his thoughts well before saying something. How should I approach talking to him and/or my FI and future mother-in-law about making sure he doesn't say something off-color to my family? I would also like to stop him saying these insulting things in front of me, but I'll take what I can get.