It's a bad thing to hold certain desires or beliefs in your mind, but as long as you don't act on them, bringing them into the real world, they only hurt you.
You can be positive that your "race" is superior to all others, and believe some "races" aren't fully human, but as long as that belief doesn't cause you to violate anyone else, who is it hurting?
Your private desires can be those of a pedophile, but as long as you don't act on it and harm any children, you can't have done anything wrong.
You can be full of authoritarian and statist delusions, but as long as you don't use violence against non-archators, nor send others to do so on your behalf, the malware in your mind isn't violating anyone.
But, can anyone honestly believe something without acting on it? It is hard to hold a belief without putting it into action. It would be best, by far, to purge that kind of thing from your mind altogether.
But, if you can't, the next best thing is to make certain you never act on it.
The problem is, if you truly believe something, you're not going to be very motivated to not act on it. You'll believe you are right and those who oppose your beliefs are wrong. You'll see yourself as the victim if you get caught putting your beliefs into action and have consequences. Your only motivation will be to avoid the "unfair" consequences of being caught.
And this is why criminalizing self defense is always wrong-- it empowers those who believe they are right to violate certain people in certain situations. It is also why no one has the right to violate the right of association for any reason-- if someone holds beliefs you don't like, you should be able to choose to avoid them.
Ultimately, it is why it is best to not hold beliefs that justify violating others in the first place. They damage your mind, they will convince you to act on them, you'll believe you did nothing wrong when you do, and (hopefully) there will be consequences, regardless.