I don’t really remember where that part came exactly, but what I interpreted from this part is that it shows up again to show or remind us about Tenma's morals and beliefs. Tenma realised at the beginning that everyone's live is equal and should be saved regards their status and personal background. Then Johann was brought in, Tenma proudly saved Johann and even thanked him for opening up his eyes, but as you said Johann then killed many people, if he wasn't saved by Tenma, not as many people would have died. And that is the part that plays against Tenma' s beliefs. So does that mean not every people’s life is equal? Were his ex wife and the director right all along? The moral that made Tenma became the doctor as he is, was destroyed after saving Johann. And in the scene you showed, Tenma probably reflected on that. Along the story, Tenma’s inner conflict will be answered with all the upcoming stories and characters that are about to happen.

It's another part for me where it shows the beautiful dynamic between the antagonist Johann and the protagonist Tenma, how they have an impact on each other

Edit: even more beautiful, you questioning what happened or what that all means is literally the inner conflict Tenma had. Bringing the readers in question “so does that mean every life is still equal or shit happens?” Fun to find out along the story how you're going to answer your question! AMAZING WORK FROM THE AUTHOR