First watch the video.
See all those white people bringing guns to the town hall meeting?
Now watch this video of the same rally, same guy, same gun.
I have three points -
1) It's not a good idea to bring a weapon to a town hall meeting or a rally where the president is speaking. I don't care what your right is; it's a security threat against a high-profile target. You also might cause some liberal to die of a heart attack, which is an unacceptable means to increasing our chances for victory in future elections. STOP BRINGING WEAPONS TO THESE RALLIES.
2) MSNBC clearly did not want to show the man's skin color in their edit of the video because then their whole "angry, white, old people want to kill Obama because of health care" narrative would be shot, if you'll pardon the pun.
3)Zombie has an interesting piece on this topic where he shows lots of pictures of people threatening Bush. For example:
It looks like some of them were African-American and Hispanic. Are we to assume they hated Bush because he was white? Or maybe we should take a cue from MSNBC and just crop the images with the white people in them and imply everyone who opposed Bush was black or hispanic.