Why is it considered 'racist' to say that Western civilisation is superior, even if that's downright true?

First of all the West is not the best. I can tell you know each culture has its highs and lows, and the most DOMINANT cultures are actually the worst. Governments are evil too, and the west has not achieved the most in art,science, or any of those things. You should respect other cultures and other people, I know hundreds of people from other cultures, they all think there country is better, how about some reality okay?