If Harry Victor was indeed "photographed for Life getting tear-gassed in Grant Park" during the 1968 Democratic Convention in Chicago, he was among the protestors pictured here (49).

Wikipedia recounts the Convention thus:

Anti-war demonstrators protested throughout the convention. Initially the protests were uneventful, but tempers gradually heated, and soon police and protestors were clashing all around the convention center, the Chicago International Amphitheater (in the streets, as well in Lincoln Park and Grant Park). Daley [mayor of Chicago] took a particularly hard line against the protesters, refusing permits for rallies and marches, and calling for whatever use of force necessary to subdue the crowds. A 1968 Time article noted that "demonstrators constantly taunted the police and in some cases deliberately disobeyed reasonable orders."

Despite the poor behavior of some protestors, there was widespread criticism that the Chicago police and National Guard used excessive force.