I think his supporters want him to screw with treaties and tariffs.
A president only needs to be as smart as the folks who elect him. I guess they don't know anything about the impact of Smoot Hawley.
As regards Trump's statement about whether the US kills people it considers its enemies - it does. That's what the drone programme is for. The question is, does it try to avoid harming innocent people while doing so? I believe it does, generally. And this makes it different to Putin who seems not to give a damn. But things don't always go as planned.
I'm not such a peacenik that I am against killing bad guys in lawless areas. But where there are laws, I prefer prosecution.