I work with a know-it-all. I get long lectures about everything under the sun. Sometimes it's just flat-out wrong information. Other times it's bits and pieces pulled from the internet, particularly Wikipedia. It seems to me this person has an extreme need to appear knowledgeable--about everything. Nothing I say will make it stop, so I try to avoid having to listen in the first place and respond blandly "Oh? Huh" in the second.

You might try this, with one caveat. If the person is suggesting something that will bring harm to him or herself or others, calmly bring it to the attention of one of the experts--then let whoever that is handle it.

Sometimes people don't know what they don't know. And sometimes they are blow-hards. It's perfectly fine for you to reply "I've been doing this for a few years and I still feel like I am learning the ropes" or to say nothing at all or to refer them to the experts.