Open this photo in gallery: Fred Hahn, President of the Ontario Canadian Union of Public Employees (CUPE), speaks at a press conference at Queen's Park, in Toronto, on July 16, 2018.MARK BLINCH/The Canadian Press After a public backlash and calls for his resignation, the vice-president of the largest trade union in Canada has apologized for posting a social media message celebrating “the power of resistance” the day after Hamas militants slaughtered Israeli civilians. CUPE Ontario president Fred Hahn expressed his regrets as politicians and university student unions are facing pressure to walk back comments that have been interpreted as justifying...