Relative to what he 'should' have done Marcus' actions are clearly wrong. That isn't in dispute. The point is why he believes his way is the best way for the Federation. He has his reasons for making his choice and his point of view. And which lines he's willing to cross in the pursuit of those views.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist