Correct ideas bore out in reality. This is undeniable. Correct analysis will be correct, and flawed analysis will not. This works out in Marxism's favor, because it is an extremely powerful analytical tool.
With regards to speaking to non-Marxists, following the previous paragraph, you can describe concepts without giving away their origin. Point out Monopoly Capitalism as it relates to Modern Imperialism and is the driving factor of modern conflicts, without pointing out that it was Lenin that put pen to paper on it a century ago.
You can also take advantage of "common sense."
Sounds like Harris needs to try to win back disaffected Muslim-Americans turned away by her promise to continue genocide.