1:

"focus on the idea that there was racial and religion..." That there HAS BEEN racial... since the past.
"21st century which..." After "which" should be a separate sentence.


4:

"the liberated, the mistreated, and the dehumanization..." No coherence in the list. (liberation, mistreatment, and dehumanization?)
"lowest part of the totem pole." Bottom of the totem pole

5:

"black people because the images they were portrayed." Either:
1) they were portrayed IN (not so good)
2) because of the images in which they were portrayed
3) because of the way they were represented/portrayed (visually/in images)

"more evident when he is fascinated..." As he is fascinated by the realization

"In the context in..." Scrap the initial In: "The context in which"

6:
"He displays..." expresses/remarks/comments on?
"they must be prevalent..." they must prevail
"Being black was working towards..." was= means?/is?
"have used all the negativity to shape them": Use is an agentive verb, which denotes action. It reads as if black people did the action consciously, which I think is not correct. You could rewrite it as "black people have absorbed all that negativity and it has shaped them into...". That way it makes it clear that black people are not responsible for their present shape.

Conclusion: Understanding past racism (irish) and present racism (blacks) may help to understand the idea of racism more deeply, which should lead to better, more informed fight against it. ("being named black was just someone's name for being at the bottom")