Wow! is the interjection because it is a word (interjections may also be phrases) separated from the sentence by an exclamation point.
Metaphors to compare equality to things the audience knows
Explanation:
When an object is compared to an action or a phase in which it is not applicable then it is called as a metaphor. In the except President Kennedy mostly conveys his points by using metaphors to compare equality to the audience so that it can be easily relatable.
Americans in the early period suffered from the inequalities done to them. Most often the black Americans were subjected to this type of activities.
Several ways you can determine the validity is
1.) The author and his credentials.
2.) Sources that back up the article/publication.
3.) Whether the article features bias or none, when appropriate.