I think that if your government is basically a protection racket, extorting resources from its subjects while providing minimal benefits, then refusing to pay taxes seems pretty ethical to me.
But if you think your government is, overall, something that you would rather preserve than destroy, then I think the ethical case for paying taxes is pretty strong.
Most people would say that you shouldn’t steal, murder, cheat your business partners, etc. even if you could get away with it and donate the proceeds to charity. I think the widely-accepted justifications for not doing that are, broadly:
Some form of deontology that says you need to follow those basic rules of fair play even if the utility is not great.
Consequentialist reasoning that breaking these rules damages society’s ability to coordinate around the rule that was broken (and, to a lesser extent, to coordinate around any rules at all), and this societal ability is so immensely valuable that this outweighs other considerations in most realistic scenarios. (Especially considering that your lying brain will exaggerate the societal benefits of anything it thinks is in your self-interest.)
If you accept either of those arguments for not robbing a store, and you think your government is on-balance good to have around, then I think you should also accept those same arguments for paying your taxes. If the government is basically legitimate, then evading taxes is pretty similar to theft. At minimum, it’s defecting from a societal rule that is widely considered important and which has been thoroughly ratified by our standard societal-rule-process.
The consequentialist bullet-point above is similar to the ethical objection that you argue against in the OP, but I think you’ve imagined the commons-being-damaged too narrowly and thus significantly underestimated the value at stake. For instance, maybe you think our current tax rules are bad, but perhaps you’d like the ability to have and enforce any tax rules at all, even when some of your fellow citizens disagree with you about what rules are ideal. Will you be able to have that, after establishing that you think it’s OK to refuse to pay taxes just because you think the current system is inefficient?
I also think this specific objection you make is very far-fetched:
Why exactly should I expect the rule of law to collapse (rather than for the government to be reformed or replaced) when the consent of the governed wavers: could the results not just as plausibly be positive ones?
Imagine using this argument against one of the more widely-accepted rules I mentioned above, like murder:
Alice: You shouldn’t murder people, even if you could get away with it and the world would be better off without the specific person being murdered, because that would damage society’s ability to coordinate around the very important “generally don’t murder people” rule.
Bob: But if that rule loses popular support, why wouldn’t it just be replaced by a new rule? And couldn’t that new rule just as easily be an improvement?
Good rules are a small target in possibility-space and it takes work to hit that target. If you want to get a better rule, you’d better put a lot of effort into coordinating with other people and carefully channeling your force towards that small target. It seems incredibly naive to me to think you’ll get a good rule automatically just because you smash the existing rule.
Additionally, there must be some historical reason that we have the rule we have. For important, high-profile, long-standing rules (like murder, or taxes), a plausible guess at that reason would be that it was the best rule our predecessors could realistically get. Unless you have some specific reason for thinking you can do better than them, it seems fairly unlikely that you could get a substantially better rule even with a highly-coordinated effort.
Bob is also imagining this as a clean switch from rule A to rule B, whereas in reality there will probably be a long period (maybe indefinite) when rule A is damaged enough to become less effective but not damaged enough to collapse.
There’s also inevitable collateral damage to other rules.
You complained that the objection you were responding to seemed like a rationalization that someone would make up if they had already decided on the answer and wanted a convenient justification. But this particular counter-objection seems like pure wishful thinking to me. Yes it’s possible to imagine a good outcome, but is that outcome likely? How much effort are you currently putting into steering towards this hoped-for good outcome? Will your fellow scofflaws even agree with you about which outcomes would count as “good”?
I think civil disobedience is sometimes a good tactic for protesting a bad rule, but you should have at least a rough proposal for how you want the rule changed and an overall strategy for actually getting that change. It’s also exceedingly suspicious if your “civil disobedience” involves keeping a low profile and putting money into your own pocket, rather than making headlines and going to jail for it.
In my model, every act of societal rule-breaking slightly undermines literally every societal rule (although if the rule in question is bad enough this might be worth it). So that’s a trivial “yes”.
If we restrict things to more direct effects, I think most people are realistically going to interpret your policy as “don’t pay taxes that I personally don’t agree with” rather than “don’t pay income taxes in particular, there is something a priori special about income taxes specifically that puts them into a fundamentally different category from all other taxes, this is definitely not a category that I made up retroactively because it happens to be convenient for me in my current circumstances”, no matter how much you protest that your real policy is the second thing. Therefore if they agree with income tax and disagree with Georgist tax, they will think they can ignore Georgist tax and that you will have no right to complain when they do. So, again, yes.