I suppose it would be very difficult for us non-Muslims to add up and calculate whether Humility or assertiveness has the greater influence in Islam as a whole.
...We all know that all religions have some seemingly contradictive writings, and some are more pronounced than others.
My current view, through my own interactions and understandings of Islam, is that assertiveness is a more valued trait than general humbleness.
The more in depth my understanding of Islam's take on humbleness becomes, the more fully I will understand if Islam is truly good or bad.
Couldn't one be humble towards oneself and also assertive with regard to God's justice. A suicide bomber could be a very humble act.
I don't see humility as necessarily equating to peacefulness. A soldier could be very humble while fulfilling their duties as a soldier.