What I find particularly interesting about this is that the reason the tax was struck down is that it was deemed an "excise", which only the Commonwealth can impose. But also that the result was very close, 4-3. I'd love to hear what lawyers think about the case from a strictly legal perspective.
From the moral perspective, sooner or later we will need to have something like this. Cars are insanely expensive on society and on our governments, and putting as much of the charge on their users as possible is just good governance. But as much as all cars are bad and electric cars are cars. The electric part of electric cars makes them slightly less bad than ICE vehicles. So their uptake should be encouraged relative to ICE vehicles, even while policies encouraging public and active transport should be the most supported.
Add an excise like this once EV uptake is upwards of 50% of new vehicles, not right now. If you want to help your government's budget, try subsidising ebikes more and encouraging their uptake by mandating every route have safe separated cycleways. That will reduce damage done to the roads a lot more than the fraction of repair costs this excise would have delivered.