Who do the colonists blame for these injustices ???

The colonists are blaming the King for their grievances because he is doing things very unfairly; without proper representation, he doesn't really think about the colonists and how they feel about the matters, he just does things without consent

( if that's what you meant)

so they can differentiate themselves from others as they saw themselves as the superior race. the star was basically a symbol that meant you are a less of a person than i am because of my race. the star was also degrading for those who had to wear it because they were aware of this and the nazis used the notion to make them feel less like a person.