Free trade is in moral and illegitimate when the country being used as the workforce has slavery or a near condition, abject poverty and no environmental rules.
Free Traders would not agree that it’s wrong to sell lampshades made in a Nazi death camp as long as the Jews were paid $0.50 a day. Nothing in the free Trader philosophy would prevent that. They sell Us North Korean made products today.
So punish the practitioners of slave labor. Don’t abandon what works because of one case. Free trade helps build everyone’s economy.
Slave labor isn’t free trade. You impose sanctions to force the violator back into compliance with the norms of trade.
That is a scurrilous lie, and I think you know that.
If that's what your case rests on, you have no case.