He doesn't appear to want to get down in the dirt. And in politics/geopolitics, that's where a lot of the action is.
He may wish to be a man of peace, but in the job he has, sometimes you have to have the stick. Speak softly and ...
Putin has seen that Obama is unwilling to employ US power. And he is taking advantage of it. Witness Ukraine and Syria. O's too fastidious to get involved, even when Assad crossed his red line.
Avoiding involvement doesn't mean the problems disappear. The problem of Isis and Islamic radicalisation - which grew in response to Assad - didn't go away because Obama doesn't want to intervene aggressively against them. It transformed into new problems like the refugee crisis. The child who drowned on that Greek beach drowned because politicians chose to avoid intervening, leaving the local populace to suffer the consequences.
Non-intervention leads to the appearance of millions of Moslems in Europe. Is Europe's secular, tolerant, post-War identity going to get washed away because we dare not do anything that involves fighting and killing in the Moslem world?
See Jihadism grow. Everywhere. It doesn't go away just because newspapers avoid reporting it: http://www.thereligionofpeace.com/index.html#Attacks
Sometimes ideals are in conflict. You may wish to be tolerant, but you can't tolerate intolerance. If many Islamic adherents espouse values we find abhorrent, then we must speak up even if it means we cross the apparently sacred boundary of multiculturalism: appearing to treat all cultures as equally worthy. Sometimes a culture (or a portion of a culture) is toxic to those around them. Obama pretends Islam is a religion of peace. Maybe he has to. Sanders closes his eyes and pretends it's all okay. The result: they don't do anything but wish.
Who are the victims of the unwillingness to argue/fight with extremist religious fanatics within Islam (which appears to be a large slice, unfortunately)? Moderate believers. Pretending it is all okay, washing your hands of the problem, causes its own harms.
Obama is fastidious. No dirt under those nails. He values virtue over pragmatism. And bad things happen because of it.