I looked for a tax ruling and court cases and came up with the ruling listed at the link. This is only recently posted to the public information. It represents new information for me, and I have to modifiy my original response based on that. I apologize.
The IRS Agent may be right, in this case. In prior years, (last year), the IRS had allowed some clients to take NSF deductions as interest, because their banks had expressed the NSF fees as an interest rate.
However, in a more recent ruling this year, regarding NSF for checks written on bank credit card accounts, (convenience checks), the IRS ruled that NSF fees were not interest for IRS tax reporting purposes.
This is a ruling from January 17, 2007, and was just recently posted in an update to the IRS website.
If the NSF are not counted as interest for tax purposes in general then it holds true that you would not be able to take them as a deduction.
If the NSF are not counted as interest for income, then it also holds true, that you would not be able to deduct the fees.