A purchase-price rebate enables manufacturers to get away with higher EV prices than they would have to in competitive market.
If you impose a tariff on ICE imports (new or used) then you don't make EVs cheaper, just ICEs more expensive. Cars on average cost more and fleet modernising (which also reduces C02 emissions) slows down.
What is needed is for EVs to be cheaper to buy. And have increased range and/or faster charging. And have the same standard of fit out as ICEVs. Hyundai is actually pretty good at having a consistent fit-out of safety options across model variants.