To clarify, or rather to state the obvious but implicit subtext in the remarks to date, the marketing firm claiming the name Radical Media would probably not win a law suit (at least not under US law, though granted they are international).  It would be hard to prove that a comparatively small conference of academics and other leftists and radicals in any way dilutes their brand!
 
But their attorneys expect never to go to court on this.  They know that the legal fees, regardless of outcome,  would be punitively costly to conference organizers, whereas they, the attorneys for the marketing firm, are already paid for, either on staff or on retainer, and must prove their worth. 
 
An information campaign is a great idea.  And by all means all of us should contact them, but do so strategically.  Don't do it to express outrage, or tell them that they are wrong--they don't care!   Do it to convince them that their actions will prove unprofitable.  Their web page--http://www.radicalmedia.com/--under "about" about, lists their CEO and other officers, with a direct links to their e-mail.  They also have phone numbers for their New York offices.  They are international--contact the officers nearest you, in their own language, or contact them all.  And do it more than once. 
 
And if a protest is organized at their headquarters, it doesn't really matter whether 40 or a thousand people show up.  What matters is getting media coverage.  They don't care about what is right, they don't care about what we think.  They do care about convenience, PR and public opinion.  We don't have the resources to win this in court, so take it to other venues.
 
Chris Richter