If you decided tomorrow to be an out-and-out, self-declared white supremacist, then what would you do differently?
If you already spend your time e.g. writing articles about how touchy-feely liberalism puts everyone at risk of being beheaded by crazed Jihadists, or discovering who The Real Racists are by sharing dodgy comments made by black teenagers, or continually retweeting news stories about Muslims being convicted of crimes, or angrily focusing on Mo Farah's alleged steroid use while wholly ignoring similar stories about non-religious athletes, or calculating the percentage chance of a random male being a sex offender by controlling for country of origin....
Well, my point should be fairly clear. From this baseline, it's difficult to see how you can take it up a notch to actual declared white supremacism.
If you're already carrying on like this, and quite gleefully too, then the difference between your behaviour and what you'd consider to be provably bigoted activities is pretty academic. You could maybe be a bit more conspiratorial or wave suspect flags or use racial epithets but ultimately, these are differences of tone rather than content.
So I suppose the question is: If the only way that you could be more openly prejudiced would be to do exactly what you're doing but slightly more so, then why the hell would you bother getting pissy when people tell you that you're racist? The line you're attempting to draw is so impossibly fine that it may as well not exist.
And this is before we get onto one of the iron rules of public conduct, which is: You don't have to be racist to be an arsehole, nor do you need to be a strident bigot to be a really unpleasant person to spend time with.