This isn't how markets work. Your argument is basically equivalent to the old "my vote doesn't count" line, but yet still different people get elected over time.
It's not about whether you or I buy a used petrol car over a new EV; it's about whether you & I buy a used petrol car over a new EV.
Emphasis on the environmental efficiency of new products in general over the environmental impact of buying new in the first place is a topic that's well worth highlighting.
Cars enter the world by being made, not by being sold. They leave the world by being damaged beyond economical repair, not by being bought.
This is not the same as party politics, even though literally every election and referendum I have voted in would’ve resulted in the same winner had I not voted. The political comparison would be voting ex-politicans off X-Factor or Strictly Come Dancing or $COUNTRYs-got-talent etc. (second hand) versus current politicians in elections (new).
They don't get made if they won't be sold. So if enough people didn't buy them, they would stop making them. Similarly, if enough people participated in voting for real change, perhaps we would see it.
That's the argument anyway. Personally, I think such coordinated effort is too hard to pull off because you are up against highly sophisticated media campaigns paid for by politicians and industry.
You should compare like for like. Second-hand BEV vs. second-hand ICE, or new BEV vs. new ICE. Mixing them means you’re putting all the market boosting on one product category and all the market reductions on the other category.
To put it another way: how would you react to a study which compared the environmental cost of a second-hand BEV to a brand-new ICE?
Depends on what the study is trying to prove. You seem to be angling for some sense of "fairness", as if this is a game where EV / ICE "compete" and we want the rules to give each side equal chance or something like that. This isn't sport; if you're doing a scientific study you only care about getting the correct answer to your question.
If your question is whether a second-hand BEV has higher / lower environmental cost, why would there be a problem doing such a study.
It's not a foregone conclusion either; e.g. (hypothetically) a lifecycle analysis could show an EV to be less optimised for long-term use (spare parts environmental cost, etc.), compared to a new ICE with a more sustainable long-term maintenance story. This might be unlikely but you can't find answers to these questions without such studies.
The original claim was "All EV's are worse for the environment than buying a used Petrol car". If your claim is that buying a used EV will be best of all then that seems reasonable.
Also possible that if you buy the used petrol car then the someone else who would have bought it will buy a new one instead, ultimately stimulating the production of more new petrol cars.
> Highly likely a used petrol car will be bought by someone even if not by you personally
Well when the government gives people $3 billion to smash their used vehicles (C.A.R.S in 2009)rather than keeping them in the used market, it does tend to cause more new vehicle purchases.
I'm not disagreeing with your point that people will eventually buy a new car if used ones aren't available, but if every vehicle was kept on the road for 25+ years, it would lower demand for new vehicles.
A fair assessment would be a new BEV versus a new petrol versus a new diesel versus a new hybrid.