tact is not my strongest suit
There really must be a polite way to say "thanks for going to such a great effort to inform me about something I already knew", right?
(In English, by the way. There's no point in even remotely trying to convey it in Japanese.)
(In English, by the way. There's no point in even remotely trying to convey it in Japanese.)

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If they're not openly shy about it, you can even respond by asking for clarification of some point (possibly something you already know), which shows that you're familiar with the topic but consider them a valuable source. And hey, they might actually have more information. Something like, "Oh right, Obama's been elected President. Who do you think he's going to pick for Secretary of State?"
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