I think there's an argument for what Trump is saying. Tariffs mean that Americans will chose product alternatives that don't have those tariffs attatched. Possibly from other countries outside of BRICS.

IT also gives him leverage in negotiations (eg. He can offer to life the tariffs)... And gives him a way to appear to improve the economy ("oh look, things got cheaper and spending accelerated because I lifted my tariffs, ergo I'm good at economic management").