It wasn't necessary. Anyone who watched the show up to this point should have already understood what the show was about..
Given the outright denial of the presence of racism we had in this very thread, I find this assessment... poorly considered.
Try an experiment. Think to yourself, "It wasn't necessary
for me." Then, acknolwedging that it isnt' all about you, we can consider what that scene was really about, and who it was really for...
Captain America is about more than really great punching. Cap's powers aren't just about shield-slinging. His base superpower is his ability to be on the right side of any moral question. Walker failed at being Captain America because he lacks this power. In a narrative sense, Sam needed to display this power before he could really fully take on the mantle.
Beyond that, whether you needed it or not, the folks who deny racism needed this scene.
And, vastly more importantly, young viewers need this scene. Not because they don't get it - I daresay most of them get it better than we older viewers do. No matter their skin color, those younger viewers need to see an African American hero speaking moral truth to power. That
absolutely needs to happen for the overall story to not betray it's own ethos.
"Be quiet Sam, we don't need to be told this," is about the most ironic bit of critique that could be made of this piece. I mean, the Senator he's talking to tries that line... and clearly he was wrong.
So, probably when we say the same thing, we are wrong too.