This pretty much sums it up. He has every right to engage in all the racist douchebaggerness he wants to his heart's content. However, when he is speaking about the 2A in a public forum, his prior actions do speak to his credibility.
I'll be honest, I don't like racists. To me, bigotry speaks of willful ignorance and deficient intellect (you're an idiot and you mean to stay that way). If someone wants to wallow in that sort of substandard, subhuman existence, that is their right, but be a man and own up to it. If you are a bigot I don't have to like you, but at least there is a level of respect I can give you for being honest and forthright about who you are and what you stand for. If you attempt to hide behind technicalities and obfuscation, well then you get what you deserve.