my amber warning lights always glow when I hear anyone dissed as "shrill" by the punditocracy :-)  it's a highly gendered word and usually carries connotations of sissiness, unbalance, infirmity of purpose, "hysteria" -- in short, being a "girly man" (or just plain being a woman).

I suspect that absent the most impeccable macho credentials, whistleblowers are likely to be perceived as Sissy (and hence shrill rather than "hectoring" or "relentless" or "loquacious" or "didactic") because one of the vaunted virtues of masculinist culture is Loyalty (and Omerta).  anyone who demonstrates the flexibility to change his opinions, to deviate from absolute conviction and loyalty to the Team, is a bit suspect in the Manliness department;  and more often than not will be accused of "shrillness" (literally, a high-pitched and piercing vocal quality like that of an angry soprano or mezzo, or an overexcited child).

now, whistleblowers often are -- for good reason -- passionate, aggrieved, and obsessive, accustomed to arguing from a defensive position, accustomed to not being believed and having to thrash their way upstream just to get heard, let alone achieve any credibility.  they often can't stop talking once they get any chance at all to make their case.  but this rather desperate or overemphatic tone is characteristic of just about all "Davids" engaged in intense struggle with a Goliath;  and since it comes from a consistent experience of battling the overdogs from an underdog position it shouldn't surprise anyone that we leap to cultural metaphors of femininity (or childishness, which in patriarchal discourse is the same thing) to describe (and subtly to cast aspersions on) the person thus struggling, and marked by their struggle, with entrenched power.

an interesting sociology experiment is to survey the punditocracy's utterance (from right or left field) for statistical incidence of the word "shrill" and see how often or consistently it's used to dismiss or show condescension towards (a) an ideological opponent, (b) an outsider or underdog in conflict w/ the mainstream culture, (c) a female of any stripe.  how often are Bush's obsessive and relentless (and somewhat desperate) harpings on "freedom" and "Al Qaeda" called 'shrill' by the media talking-headocracy -- despite their distinct whiff of desperation?

The difference between theory and practise in practise ...