So as a resident of a country that had it's first legal gay marriage in 2001 and universally legal gay marriages in all provinces and territories in 2005. Here are the things that have happened to marriage since:
1. nothing
http://www.theglobeandmail.com/commentary/gay-marriage-is-a-non-issue-in-canada-but-it-still-riles-america/article10193881/
Extending civil rights to all does not harm anyone.