Seriously? Well, obvious on it's face this is an absurd claim to make. I mean, come on. Right? We can all agree on that. Can't we? It's like trying to claim something like the sun doesn't rise in the morning. Anyone seeing the sun up in the sky knows it not true. Similarly, anyone that's engaging in discussions where they're disagreeing with a liberal without being called a racist most know this. Right? So then, why would anyone that isn't being called a racist in real time while disagreeing with a liberal claim it happens every time?
Society has gone through a stage where in a debate/arguement/whatever, liberals have often defaulted to shout such words as racist, bigot, xenophobic etc... The two current ones are homophobic and Transphobia. They're overused and eventually lose their effect. If you're on forums debating, it's likely you experience these quite often and thus that person feels they're always used.
Without a doubt, there are false claims of racism. But actual racism is also dismissed away or minimized even when it's blatant and obvious for political reasons as well. That happens right here on this forum too. Like in the last sentence of your post.
But claiming that everyone who disagrees with you politically always calls you a racist is just laughable BS. The goal of people who make that claim is simply to gain sympathy and to change the debate.