Get rid of Mail VIP list
What most likely happened is, somehow, you clicked on a star icon which appears just to the right of the senders name. I've done this myself, more than once, thinking it was a bookmark / favorite button.

That star sets the sender as a VIP – an easy way to filter emails from important contacts, which is really what the VIP under the hood.

The reason it was empty is, I assume, because there were no Angielist emails in your inbox.

To remove, and I'm assuming you found this already, is by control-clicking on the name in the VIP list and selecting Remove VIP. Restart Mail once and the VIP sidebar item should be gone for good.