The part where they are similar is that both the far left and far right are willing to use authoritarian violence to achieve their goals. And the representation of the left as just "oppression is bad" is overly simplistic. They too believe in oppression of particular groups (see oppression of academics/scientists/bourgeoise/etc in almost all communist take-overs). Centrists can also have very differing views as well but the reason they are located where they are on the horseshoe is because they would rather problems be solved with slow beauraucracy/well-defined protocols and not revolution or political violence.

This is not an admonishment or support for any of these things from me personally. I personally think a little revolution is needed once in a while. Just pointing out in more detail the idea behind horseshoe theory.