Things You Don't Talk About in Polite Company

Here are the hit batsmen per 100 innings pitched for selected pitchers through the end of last season:
Pedro Martinez--4.76
Roger Clemens--3.30
Curt Schilling--1.51

And some pitchers from history whose reputations were as headhunters or as wildmen on the mound:
Don Drysdale--4.49
Carl Mays--2.95
Nolan Ryan--2.93
Bob Gibson--2.63
Sal "the Barber" Maglie--2.55
Juan Marichal--1.14

And for fun's sake:
Jack McDowell--2.54

Which doesn't mean that Clemens is a headhunter, merely that Clemens' hit-by-pitch numbers are not unusual for a pitcher with a headhunting reputation and a "haedhunter" may not be the (good) pitcher hitting the most batsmen.

McDowell seems to think that a "headhunter" will necessarily hit more batters than other pitchers or that wildness is best indicated by HBP, although he is at least smart enough to not try to compare a pitcher like Clemens to outright scrubs.

A headhunter, rightfully so in my opinion, seeks to control the plate and to intimidate. This doesn't mean going out and hitting someone just because he can. Ideally, it is a conscious, reasoned choice rather than simply evidence of a mean streak. A brushback pitch isn't necessarily meant to hit, so they won't necessarily rack up hit-by-pitch numbers. And if the pitcher actually hits a batter, well, it just takes one or two early in your career to establish the proper reputation, which isn't really going to affect your career HBP by that much.