This is an extension of the whole “Three Felonies a Day” idea: it’s likely any prolific account will violate Twitter Terms of Service at some point, so you can target almost anyone by looking hard enough.
And Twitter is likely to look harder at reports from the FBI than your average user, therefore the FBI has more influence over who they can silence. Maybe they’re abusing it, maybe they’re not, either way it feels improper at best.
You’d really suggest that all reports must be treated equally?