"Both sides" as a definition, before you ever make comparisons, is already a diminutive of reality. The idea that there are only ever two viewpoints, despite the reality of the current American political situation, is naive at best. Even within the two major US parties there are fractious and conflicting personalities.
The "both sides" argument isn't asinine because it equates the two major players, its asinine because it accepts their premise that they're the only ones that matter.
The "both sides" argument isn't asinine because it equates the two major players, its asinine because it accepts their premise that they're the only ones that matter.
It could, but the former is predicated on accepting the latter as fact. Argue about the former all you like, you're basically already arguing that your opinion doesn't matter because you only get two options anyways.
If your argument were "There are only two sides that matter when voting" it would still be wrong, but at least it would make sense. Voting matters, but it isn't the only thing that matters.