if someone was to film & post my original interview without my permission, is that a copyright violation?

Nope.

Copyright is granted to you for art or creativ work that YOU create.

The video they posted is something THEY created.

- Stuart

Yes, in fact, it is a copyright violation. But it's an odd dilemma: you don't own the physical recording, but they still need your permission to publish (upload) it.

You own the creative content of the words you spoke that day, as a matter of law, but only when they were recorded. The other person owns the only existing copy, but you still own the copyright of anything you said. For the purpose of copyright law, it doesn't matter that it was in public! They have no legal right to publish a recording of your creative work without your permission and you can contact YouTube and complain that you are the copyright owner of the underlying work and have the video removed immediately, under the DMCA.

In fact, there is a special copyright law for "live music performances" that makes it a copyright violation to record it (wherever it is) without permission of the performers or to duplicate or distribute any such video. "Free speech" has nothing to do with it. So, like your own case, they can't say, "Oh, but it happened in public so it's not copyrighted." Sorry. They lose.

I used this as an example in class when I taught Intellectual property at a university. "How many of you are recording what I'm saying right now? Who do you think owns the copyright of the sounds on that recording? Knowing that copyright is automatic when you record something, would the answer change if every word I am saying were already written down by me or recorded by someone else before I said it here today? And, who would own the copyright of THOSE writings and recordings?"

If it was a public event that they filmed, they can do whatever they want with the video. It's protected by the First Amendment. You never copyrighted any material, nor had a right to.