If I, as a voter, voted for a politician who promised to ban dumping mercury in the local river, I don't expect them to say "Oh, but any company already dumping mercury in the river can keep doing so, because we don't want to hurt people's livelihood." That's not what I voted for.
His point was that they were grandfathered in for making cars in general. But he flat out lies about making batteries being something grandfathered in. That wasn't a battery manufacturing plant to begin with.
And he further lies to say they had to build elsewhere because cell manufacturing was "effectively impossible" because they expanded the factory for cell manufacturing in 2023. [1]
[1] https://electrek.co/2023/06/09/tesla-snaps-new-location-frem...