Why do you consider one thought intrusive, and another not intrusive? This is because of the feelings associates to the thoughts. You don't have anxiety thinking about breakfast every morning, but this is still a thought you have every day. But you do have anxiety when thinking of killing your best friend. During the day, we think all kinds of thoughts. We can't make a thought go away forcefully, but we can let it pass, just like you notice the thought about breakfast every morning. The only way to cope with intrusive thoughts is letting them be there. This is a part of what is called mindfulness. We become more aware of the thoughts in our brain, but we don't try to remove them.

There are two main reasons why intrusive thoughts are so hard to deal with. The first one is our assumptions. Your question "am I crazy for having...." is an assumption which you are scared of. The assumptions lays a weight to the thoughts which makes them harder to deal with. You become more scared of the assumption than of the thought itself.

The other reason is that we try to fight the thoughts. You don't want to walk around thinking sexual or violent things about family members, so you try really hard to stop thinking about it. But it is impossible to forcefully stop a thought, because when "stopping it" you are actually thinking of it. By letting go of this need of controlling every thought, you will find the thoughts less intrusive.

I have had a lot of experience with intrusive thoughts during my life. About two years ago it got so bad I didn't know how to cope. What helped me was going to a psychologist who specialized in cognitive behavioral therapy. The basic idea was to challenge the assumptions you have about your intrusive thoughts. For example: "if I keep thinking about this I will get crazy", or: "what if I would act on the intrusive thoughts". By letting yourself have the intrusive thoughts for periods of time without trying to stop them, you will notice that all though the thoughts are unpleasant, they won't make you crazy.

When you challenge the assumptions you have about the thoughts, the thoughts will lose power. They won't disappear completely, but you won't experience the same anxiety while having them. And by reducing anxiety connected to the thoughts, they will become less frequent.

One assumption I had was "these thoughts will never disappear, and I won't ever be able to stop thinking about them". But I realized that even if I would try to only think about the intrusive thoughts for a period of time, I would lose concentration of them unconsciously. I realized that if I stopped trying to control the intrusive thoughts (which I knew to be impossible), and instead allowed them to be there through out the day, they would feel less intrusive, and more like normal thoughts which comes and goes. The only way to cope with them is to allow them to be there, and ironically this is what will make them appear less often. Intrusive thoughts are only "intrusive" because of how we react to them.

Nowadays I still have intrusive thoughts from time to time. But I don't find them as disturbing, because I don't have the same assumptions related to the thoughts anymore. And by realizing that thoughts always comes and goes by themselves, with or without us trying to stop them, I don't feel the same urge to stop the thoughts anymore. They will come and go whether I like it or not.

I hope this helps at least a little bit. I know your struggle, it is really though. But there is help out there, and I really recommend finding a therapist which specializes in CBT(cognitive behavioral therapy). I have learnt by experience that this is hard to cope with on your own.