Here's an alternate idea, one that will have a permanent effect without damaging LJ:
For one day, make no posts. Make no comments. Let there be NO new content added to LJ.
SUP obviously does not realize that Basic users have given something of value to them, that it is content that drives the site.
So, for one 24-hour period, from midnight GMT to midnight GMT, let's see how many people we can get to pledge to contribute NO CONTENT.
This will create a permanent downward spike in the daily-posts statistics, a permanent reminder of the power of the userbase.
Who's with me, and what date shall it be?
Edited to add: This Friday, March 21, from midnight to midnight GMT.