I think you've all established that Bulwer-Lytton wrote 'The pen is mightier than the sword' in 1839, that it's now a common proverb, and that we're looking for a reversal of that proverb. I would start by taking the history of the original proverb further back.
1st century BC: 'Cedant arma togae (Arms give way to persuasion)' (Cicero).
1571: 'There is no sworde more to bee feared than the Learned pen'.
1582: 'The dashe of a Pen, is more greevous then the counter use of a Launce'.
1586: 'Alexander surnamed Severus, would oftentimes say, that he stoode in more feare of one writer, then of a hundred souldiers, for that the wound of a pen remaineth after death'.
1602: 'Many wearing rapiers are afraid of goose-quills' (Hamlet).
Before 1712: 'Poor Bob...a goosequill on for weapon ty'd, Knowing by use that now and then A sword less hurt does than a pen'.
More information than you wanted, but it shows that Bulwer-Lytton wasn't so original as all that. Now, what's the reversed form that we're looking for? I'll take three guesses:
'Let none presume to tell me that the pen is preferable to the sword' (Motteux' early 18th century translation of Don Quixote).
'Whoever said the pen is mightier than the sword obviously never encountered automatic weapons' (attributed to General MacArthur).
'The man who said the pen was mightier than the sword ought to have tried reading The Mill on the Floss to Motor Mechanics' (Tom Sharpe).
Do any of those look familiar, Mighty M?