I think it's not too much to expect to know basic terminology in a leftist space. In Argentina I've met plenty of social democrats who understand imperialism in its leftist sense, because being in the periphery means you see the consequences of imperialism, and this is a country where like 99% of the media is owned by the comprador class or international capital making propaganda for austerity, meritocracy and other bullshit.

If somebody doesn't understand why their definition of imperialism doesn't seem to be the one we use, maybe they can ask questions rather than interpret us in bad faith and so on.