What does knock smbd. down mean? To bring down hubris out of smbd.?
So I thought I’d stop by and try to be a hero. OK, if it’ll make you a hero and maybe knock Jackie down a few notches, we might be able to find something that’ll work.

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This person thought that Jackie was  conceited/a snob, so he/she thought that it would be a good idea to do or say something to Jackie to  humble her/ make her be less conceited.

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to knock smb down = сбить кого-то с ног
to bring down hubris out of smb. = сбить спесь с кого-нибудь

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In this context, I would have to agree with you. Putting them in their place; humbling them.