I've only questioned the act of immigration itself - NOT criticised any particular culture or race

To say that you're racist doesn't mean that you've criticised any particular culture or race. (While I'm about it, we're well aware that you love the world being multicultural.) You want to preserve English culture by excluding foreign influences. In other words, you want to exclude foreign people from England (from now on, if you insist), because you see them as a threat to the purity of English culture. That is racism.

Any chance of giving some thought to my question about assimilation, by the way? You've said earlier that it's a bad thing when people lose their culture; in many ways I tend to agree. But doesn't that mean that it's a good thing when immigrants keep their culture alive?