I have faith that even the most fervent liberal can be shown the error of his ways. Once a liberal is shown the truth, the fallacy that is liberalism falls apart.
Max Eastman, onetime editor of The Masses, a Maxist periodical of the 1910's, became more knowledgeable in later years. In the mid 50's, he published Reflections on the Failure of Socialism and supported Senator Joseph McCarthy. Redemption is possible.
Now course, if that doesn't work, then your plan is a good fallback position for those refusing to repent.
Committed Liberals cannot be shown the Truth because their notion of what constitutes Truth is fantastic i.e. a construction in fantasy. A philosophical liberal believes that truth is a mental construct and thus impervious to what appear to be “facts.” Truth is what a liberal wants it to be. Facts are thus illusion. If facts seem to contradict a liberal he understands only that he is not firm enough in his worldview and has not trained his mind well enough. He will work to correct that failing or he will accept that he is not perfect but will be even more fanatic in his insistence to himself that the facts are only someone else’ mental construct and not valid. He increases his volume in denying the existence of obvious facts because he fears that others will see that he does not sufficiently believe.