SEATTLE — It was major local news when the new City Council was seated here in January with a 5-to-4 majority of women.

It was even bigger news last week, when that new majority worked together for the first time — rejecting, in a 5-to-4 decision along gender lines, a land-use deal that would have paved the way for a sports arena intended to help lure major league professional basketball back to Seattle.

The resulting backlash was ugly, and swift.

In hundreds of email messages and social media posts, the female Council members were attacked by people — practically all apparently men — who said they lacked intelligence and an understanding of the importance of sports because they are women. One Twitter poster simply used a four-letter graphic insult to define them. Another man, in a signed email, suggested they should all kill themselves and “rot in hell.” Other critics, in less violent but equally demeaning terms, addressed them as “ladies,” who should “go back to the kitchen.”

In a city where liberal views are all but assumed and sports passions run deep, the attacks quickly became as big an issue — or at least just as politically complicated — as the arena plan itself.