The phrase/concept "both side ism" is a very clever bait and switch that, so far as I can tell, was designed to marginalize/discredit people who are trying to actually engage with the issues (instead of just toxically emoting), and it was avidly adopted and weaponized as such. By both sides.
No, moderatism or centrism is legitimately a fallacy. The idea or intuition that, given two endpoints, the most correct position is one in the middle, is a fallacy. It depends entirely on the endpoints.
For example: the three fifths compromise. Turns out, bad. The correct answer was emancipation all along, and the 'centrist' answer was just bad. Because, well, one of the endpoints was slavery. If you 'halfway' slavery, that's still bad. There's no merits or 'well what about's when it comes to slavery.
That doesn't mean centrists or moderates are wrong - they're often right. But it DOES mean that just taking a middle of the road approach isn't reasonable. You need to actually understand why you're doing that, and why the middle makes the most sense. In some parts of the world, right now, as in right now right now, the 'both sides' argument is pro-genocide. In the past it's been pro-slavery, pro-colonialism, pro-holocaust, whatever. Plenty of really bad stuff.
So, you can't hide behind 'both sides'. You need to justify WHY 'both sides' and why in the middle is best for this particular case.
So you just did a Mote and Bailey. The initial claim was that "anyone rejecting both extremes is automatically wrong"; I pointed out that this was a weaponized defense being used by both sides to hide their BS, and instead of responding to that, you refuted the similar sounding but unrelated claim (which hadn't been made) that "the truth is somewhere in the middle".
Saying that both sides are peddling absolute bollocks is not, in any way, a claim that we'd be better off with some sort of average of the two. Both sides are mostly full of it, full stop.
Uh, no, I was responding to the notion of 'both sides ism' which I called centrism or moderatism, which is, in fact, a fallacy.
That DOES NOT mean that both sides can't do X or Y, or that moderates are wrong. What it means is there is a particular kind of person who will hide behind middle-road nothing burger perspectives, because they intuitively believe middle of the road must be reasonable.
It's not guaranteed to be reasonable. That's the fallacy. I didn't say YOU did the fallacy, I'm just explaining what 'both sides ism' is.
Now, on to you, specifically:
> Both sides are mostly full of it, full stop.
This is a nothing burger perspective. It's not interesting, or thoughtful, or intellectual, and it's barely worth the bits it's encoded in.
Yes, politicians lie. And? So what? That doesn't tell anyone anything about, well, anything.
Also, when certain politicians are lying about certain things and you say 'well everyone lies!' - you are making it worse.
You can bet your fucking ass that the reason people like Trump are able to railroad your constitutional rights is because there's droves of useful idiots who will say 'well democrats do the same thing!'
Okay? But they're not doing it right now, right? And that little tidbit doesn't magically make everything okay, right? So what have we achieved? In our quest to find the right answer, we've just justified and defended behavior that we know is bad for us. That's just self destruction.
1) The fallacy that averaging two wrong answers will somehow magically give you the correct answer.
2) The fallacy that the opposite of a wrong answer must be correct.
People who point out that partisans are committing the second fallacy are routinely accused (as you are doing here) of committing the first. This is a weaponized strategy which (somewhat ironically) employed by "both sides".
It is quite possible for A to be wrong, the "political opposite" of A to be wrong, and their "political average" to also be wrong. The correct answer, if any is to be found, may well be hiding outside of the framing that "both sides" have agreed to use. But anyone trying to point this out will be accused (again, by "both sides") of engaging in "both side ism" because it threatens their shared hegemony.
It's a stupid rhetorical trick, and adding more faux anger and swear words to your response isn't going to make me fall for it.
OP's point is that you get accused of "both sides ism" even if you merely try to examine the claims of both sides on their merits, the cardinal sin being not rejecting them outright. I'm far left myself and I've seen it plenty of time; on the left it's usually presented as, "engaging with those ideas legitimizes them".