Am I right to be angry (extremely long details inside)

Disclaimer: I’m not racist, really! So I’m not going to discuss about which race is better or anything like that. This question is inspired directly by a controversial comment I found on the net. I also don’t know what you Americans’ point of view on this matter, being an Asian myself, so please consider the asker of this question curious, not racist (or anything like that)!

So yesterday I was surfing the net when I found a video about a Japanese doing something weird and stupid (I’m not going to say what it is because it’s not important here). I scrolled down to read the comments for the video, and I found a comment that really got on my nerve. The content of the comment can be summarized like this: This Japanese is just a poor victim of a corrupted society. But look at America; it’s just as rotten. Do you know why? Because there are too many human races here in America, and each race creates so many sick products like jazz… and people seem to like them. Why don’t you just spend time reading about G. Washinton instead of listening to stupid jazz songs? Even worse, people from different races are getting married, producing “mixed races” that don’t have half as much white gene as our ancestors. In short, multiculturalism is responsible for the corruption of American society. Where’s the respectable European culture our ancestors built gone to? Stop multiculturalism and preserve the precious white culture for our generation! I scrolled down for some comments against this freak, but what I found were a handful of comments supporting it! Some people even complimented the author of the comment “thoughtful and politically correct”. There was someone arguing against the above-mentioned comment, but he got a slap right on the face with (another) handful of comments. The last comment of the whole conversation was: ”...The white race should not be mixed with any races”.
At that point I was enraged. If those people really think white is the best race, surely they look down on us Asian as well. I nearly found myself screaming at the top of my voice: “What is wrong with you people?”
Now I finally calmed down. And when I thought back about the incident, I remembered that some supporting comments had given some solid evidence for their claim like the Blacks live a more nomadic life, or African countries have a lower life standard than European and American ones. Still, I cannot seem to recover from my rage.
So am I right to be angry?