Purely based on the article and the little information it gives, here is my take.
Bumper stickers. They can be a bit crass and kitch and often designed to shock or inflame, but ultimately it was Williams' car and his freedom of expression, so live with it. We could argue that complaining about it is Rodriguez's own freedom of expression, but claiming someone along with others should "all be shot" is pretty dump and hardly a "view" worth expressing. He should have exercised a little more thought before opening his mouth. I think that was a bit of a reflex arc, "brain bypass" type remark. What was the point? Did he really think Williams would see the light and remove the sticker?
It seems to me politics can be a pretty divisive issue in the States: lots of very strong opinions. Have a bumper sticker? Expect reactions. Secondly when someone comes out with a stupid reaction as above: ignore! Seems he too had a "brain bypass" moment when he let himself get embroiled. As for the gun... everyone on here seems to agree: if there is room to walk away from the situation, take it as drawing should be a last resort. He didn't.
Finally, I think one key to successful CC is only ever draw in fear (fear for yourself, fear for others), not in anger.
(the article doesn't say he drew in anger, but I don't buy the "I thought he had a gun/knife" If that were true, the last thing you'd do is close the gap by sitting on him...)
Conclusion: neither was a bastion of common sense, but of the two the gun-owner will be guiltier in the public's eyes, unfortunately.
When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic.
Freedom: Please enjoy responsibly.
Any idea that relies on murder for its survival in intrinsically weak.