Yes, you CAN be racist against Muslims (and Jews)!
Just a quick note about the notion that racism is only about prejudice against people of color, and you can’t call bigotry against a religious group racism. The notion that people can’t be racist against Muslims because Islam is a religion and not a race reflects a mistaken understanding of what race and racism are. Race is not a biologically real thing — the trait most often used to define membership in racial categories, skin color, is on the whole not correlated at all with other biologically based traits. Race is socially constructed, not biological. And how people construct races is flexible; it doesn’t have to revolve around skin color.
Moreover, not everyone constructs races the same way. Just because YOU don’t think of Jews as a race doesn’t mean that Nazis don’t. They do (whether they admit to it or not). Regarding Jews as inherently inferior to “Aryans” was the whole basis of anti-Semitic discrimination and, ultimately, genocide in Nazi Germany, and it is the basis of the anti-Semitism that exists among most fascists today.
Anti-Muslim bigotry is no different. And the fact that a pretty sizable majority of Muslims in the world are people of color makes it that much easier for fascists to think of Muslims in pretty much the same way they think of black and brown people generally — though it doesn’t stop them from racializing, regarding as inferior, and hating Jews that most Jews are white. And there are many historical cases of groups of people “racializing,” regarding and treating as inferior, and even committing genocide against, groups of people who don’t really look any different from them — the Hutus against the Tutsi, for example. Race and racism aren’t only based on what people look like.