Are you sure you weren't using a VLC clone that added this stuff? Because these things exist (e.g. "VLC plus"). They're basically malware, tricking people into downloading what they think is the genuine article.
I found this thread from 2012 while researching my post. There are in fact not a lot of posts about this topic. Are you sure these entries are sponsored? It doesn't say sponsored in the screenshot.
It's been half a decade since I last used VLC and looked this up, but I'm certain there was a VLC staff member, perhaps a moderator, who explained the presence of these sidebar entries as measures to cover development cost.
There are in fact not a lot of posts about this topic
Well, a couple of minutes on Google. I just looked at all results for "sponsored" on the forum and it is in fact the only thread that uses it in that sense.
I'm still waiting for any concrete evidence, as I am genuinely curious what kind of sponsorships of that kind there are, or were, if any.
They have "Jamendo Selections" nowadays, but that service offers independent music under creative commons licences, you can also right click and remove it.
This list is filled with a LUA script in a VLC dir, and you can override it with a user list. IT's not available through GUI but if it bothers you it's possible to remove it entirely that way.