What's Mallard raving about today?
I will accept the comparison between John Brown and the man who shot Dr. Tiller. Both were murderers who engaged in terror tactics. The justice or injustice of their cause makes no difference.
I would be reasonably sure that anti-slavery rhetoric did come in for blame, and perhaps some some of it deservedly so, although I am not a historian of the period or subject.
On the other hand, unlike John Brown, we know the terrorist who killed Dr. Tiller is that he was subject to a 24x7 stream of "mainstream" commentators on television, using eliminationist rhetoric to reduce their political adversaries to sub-human status. Historically, the use of such rhetoric has incited, and continues to incite,misguided fanatics who put rhetoric into action.