I can understand how ‘tainted blood’ would be insulting. Some mixed race people might feel a sense of not belonging to either side or either culture and there are those insecure feelings of being unwanted but one must understand why some people feel distrusting of white passing people and white people. These are cultures that are exploited, oppressed, and even fetishized, so not trusting/accepting every person is understandable. My only advice would be to work on accepting yourself and if you are attempting to reconnect with one of your lost cultures then do so respectfully.