Here's a more up to date overview of the issue:
Super Bowl Sunday, Domestic Violence & Your Health | World of Psychology
The article says it was "largely debunked" and points to
this study published in 2007 that found no substantial link with increased domestic violence activity. The "largely" qualifier is due to the study RichieGB posted, which found a small link, with the note that that study was not peer reviewed. But any way you look at it, there is no evidence SB Sunday is the worst day of the year for domestic violence and plenty to suggest it isn't.