I have done some work on this. I don't think this is an era when pitchers are afraid to throw inside or hit a batter. Here are some findings, in no particular order:
From More On The Changing Historical Relationship Between Walks, HBPs and HRs
-There is a significant positive relationship between a pitcher's walk rate and his HBP rate
-In the 1960s, a pitcher who gave up more HRs hit fewer batters but today a pitcher who gives up more HRs hits more batters.
From The Changing Historical Relationship Between Walks, HBPs and HRs
-For both leagues, the HBP/Walk rate has been rising since 1980 (so poor control is not the only reason for more HBP).
-In recent years (up through 2007), the HBP/HR rate has been relatively high, even adjusting HBPs for control as measured by the walk rate.
From Do Sluggers Get Hit By The Pitch More Than They Used To?
-players who hit HRs more frequently are now more likely to get hit by a pitch than in the the 50s, 60s and 70s.
-hitting a HR in the 1990s was 83% more dangerous than it was in the 1960s in terms of causing the player to be HBP.
From 2000-2009, here is the equation
HBP% = 0.0477*HR% + 0.009
The denominator for both HBP & HR was AB + HBP. The t-value for HR% was 1.97. The equation from the 1960s was
HBP% = 0.0311*HR% + 0.0058
Since .0477/.0311 = 1.53, it means that hitting a HR from 2000-2009 was 53% more likely to get you hit by a pitch than in the 1960s.