WATCH: Teen Uses Bar Mitzvah Speech to Call for Marriage Equality

The case for marriage equality is so important to 13-year-old Duncan McAlpine Sennett that he used his Bar Mitzvah to deliver a persuasive argument to his guests.

It's been such a success that more than 20,000 people have already watched his five-minute talk at the Congregation Beth Israel in Portland, Oregon. Voters there will soon consider whether to make same-sex marriage legal.

The speech even got the attention of out actor Alan Cumming, who shared it via Twitter with this note, "Duncan McAlpine Sennett! You are an inspiration to us all. And surely mostly Scottish with that name? Bravo."

Sennett says those who disagree with him on marriage equality often claim "traditional marriage" is between only one man and one woman. But that's not what he found in his reading. "The definition of traditional marriage has changed a lot since the days of the Torah, so why can't it change just a little bit more so everybody can marry who they love?"

Watch the complete video below.