What's euphemistic about it? I used the same intensity words as your description (literally the same words, like "invaded") and mention a superset of the information (I asserted that the ban was primarily intended to combat their opium epidemic, as opposed to e.g. hurting British interests).

It's circular to bring up the US War on Drugs to support the argument that the opium wars were about national security, in response to a comment challenging whether the opium wars support the argument that the US War on Drugs is about national security. My whole point is that I'm skeptical of the case that either is about national security.