Union apologists will note that the history of labor strife is rife with violence inflicted on striking union members rather than by those members. This is true. Such violence led to laws increasing worker rights to organize.
As unions grew in strength, a tide turned and the balance was tipped toward labor. Efforts to restore some balance — such as right-to-work legislation — are being met with fierce resistance. When that resistance includes thuggery, labor has gone too far.
Public officials, starting with President Barack Obama, need to unequivocally state that union violence in any form is an unacceptable means of pursuing or opposing political change.