Oh, it was perfectly understandable to me too, even though I am not a native English speaker (but I have been told by native speakers that my English is quite good).
"Everybody" seems to be in the third person and "you" is in the second person, so I thought it was a mismatch (since in the same sentence, etc.), and so was ungrammatical.
Let anyone tell me if I am wrong, would like to know.
Real world grammar is a lot more fluid and flexible, than just blindly following a bunch of fixed, mechanical rules.
The mechanical rules are just an imperfect attempt at capturing parts of the richness of real world language, or more precisely: language variants of different dialects and speakers.
Of course, there's a whole world of class markers overlaid here as well. If you want to sound middle-class educated in most of the English speaking world, you have to avoid "ain't" and say things like "It is I" or "Bob and I went shopping.", instead of the more natural "It's me!" or "Bob and me went shopping." That's what Emond calls 'Grammatically Deviant Prestige Constructions'. The whole point is that they aren't part of a naturally learnable variant of English, so they can only be acquired by schooling.
Most people who speak prestige-English over-generalise, and also say things like "She likes Bob and I.".
"Everybody" seems to be in the third person and "you" is in the second person, so I thought it was a mismatch (since in the same sentence, etc.), and so was ungrammatical.
Let anyone tell me if I am wrong, would like to know.
And see my reply to sbuk, it was just in fun.