How Should I Respond to News of a Same-Sex Marriage?

Questions about how to respond to a friend’s enthusiastic news of a same-sex marriage, whether one should send a gift to a same-sex wedding, and whether there’s any merit to Christians withdrawing from “the world” and congregating together for the purpose of safety and shared community standards.

• What’s a winsome way to respond to a relative or friend who enthusiastically tells you their child recently married in a same-sex marriage?
• I won’t be attending my cousin’s same-sex wedding, but would not sending a gift be unnecessary and rude?
• Is there any merit to Christians withdrawing from “the world” and congregating together in their own areas for the purpose of safety and having shared community standards?