I think the one with all the leftists he is debating is the Brandeis one.. An awesome display..
And the one you (original poster)refer to .. was a "National Press Club" one. It may have been red dye, but according to the person that did it, it was pigs blood. He called into a radio show when Kahane was on. The radio show producers cut him off though. The host was a bit annoyed with them, since he wanted the (verbal) confrontation.. It may have been barry farber presenting.. You can listen to kahane audio, if you google it.
Fact is, the way the leftist looked like he hit him on the head, the the red stuff poured down from his head. He - and everybody else - must have thought it was his blood..