Let's say you convinced your relatives to stop boycotting those products. Then, the CEO of a company behind one of those products, appeared at a political rally in the ex-imperial country, wearing the symbols and colors of thebold imperial regime, and waving a flag showing the old imperial borders.

I think your relatives would be quite justified in boycotting that one product.

You can make your purchasing decisions however you like. Other's don't. Ignoring war trauma makes someone a shit businessperson, at best.