The aggressor is bombing civilian knowingly and preventing them from escaping war, the aggressor is threatening NATO with nukes if they assist the people the aggressor massacres in any way.
"Continuing trade with the aggressor" is telling the aggressor they can continue the slaughter of civilians in Ukraine with little consequences. That's immoral and unacceptable.
All the aggressor has to do stop sanctions and businesses boycotting the aggressor is to stop the slaughter of Ukrainians and get out of Ukraine, it's pretty simple.