Condom puppet 

This term is not unlike 'sock puppet' but with a more derisory tone, especially in Internet forums.
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Whereas a 'sock puppet' is someone who resorts to using several screen names in order to make himself appear as more than one person, affording the illusion of there being many more posters possessing of the same opinion, a 'condom puppet' on the other hand is someone who employs the same tactics but resorts to ad hominem attacks, crass insults and dismissals, repeating the same insults with each new screen name.
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A condom puppet will usually resort to employing the same list of screen names repeatedly in order to give the impression of there actually being a different person who uses only that screen name.

Ergo, a condom puppet is someone who's a mean, miserable little prick on the inside, and is totally artificial on the outside.
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The artificiality arrives from the condom: An artificial covering.

Condom puppet by Royal Scots Highlander June 23, 2009