1
general::
Act without regard for the feelings or interests of others, as in She just forges on, riding roughshod over her colleagues. This term alludes to the practice of arming horses with horseshoes mounted with projecting nails or points, which both gave them better traction and served as a weapon against fallen enemy soldiers. By 1800 it was being used figuratively for bullying behavior.
American Heritage Idioms
2
general::
Phrase(s): ride roughshod over someone or something [and] run roughshod over someone or something
Fig. to treat someone or something with disdain or scorn. • Tom seems to ride roughshod over his friends. • You shouldn’t have come into our town to ride roughshod over our laws and our traditions.
McGrawhill's American Idioms And Phrasal Verbs