Sports celebrity worship disgusts me. It's bad enough that the local news takes time away from legitimate news to cover sports, legitimizing it. It's bad enough that people around me at work often spend more time talking about it than working. I'm thankful that Google lets me escape it, but I'd prefer that they don't "opt in" people by default.
If you click the hamburger menu at the VERY top of the Google Now page, and go to "Settings" and then "Your feed", there's a toggle switch for "sports" (says "scores and game times"), among many other things you may also want to switch off.
By default they are all on.
I made mine disappear by flipping that toggle off - seemed to be the right setting.