If your talk is in response to another talk by someone else, and you're taking slides and content from their talk and reacting to them, it's important that your audience know what the initial talk was. They have to have the context of the debate, including who is on each side, to fully investigate both sides and reach their own conclusions.
Well, maybe don't do that then. You could address the ideas from that talk instead of the talk specifically, and have a slide, like,
"My talk is a response to this other talk by this person and I encourage you to check it out".
