"Well, Bob, as your viewers may know, 'Smith Mail' came out of a group that calls themselves 'The Dark Mail Alliance'. This is a group of anti-government hackers that..."
To Euro-English speakers, 'git' is a rather coarse pejorative term for a person:
http://www.etymonline.com/index.php?term=git
It's fairly vulgar, of a similar coarseness to calling someone a 'stupid fucker' in US terms.
The in-joke being that Mr Torvalds chose the name specifically to cause offense.