An act of congress allowed the ACA, and a vote of congress was unable to remove it.
So asking the court to do what congress could not is almost the definition of legistlating from the bench.
At least be honest that both sides do it.
Would you say the same about all the civil rights cases that were only successful because the Plaintiffs went to the courts? Not always is it legislating from the bench simply because it couldn't pass in Congress. That's a statement that sounds smart but doesn't have much behind it.
I would define legislating from the bench as creating new laws or changing the law simply because you believe the policy is better. That happens on both sides but is definitely more common on the left.
And yes, saying the ACA was a tax is real stretch IMO. You might like the result but that doesn't mean it's the law.