I have violent and upsetting thoughts.

You're not the only one to have thoughts, that are unwanted and out of character for you.
For some people it can be a problem that they start to obsess about such thoughts which can help to make the thought more frequent and worse. A problem of purely obsessional obsessive-compulsive disorder, or POCD.

Why the thoughts first started to appear may be a separate question, but giving them too much attention, especially in a distressed way, can make them reoccur.

So don't worry about. Brains sure can come up with a lot of stuff, and you're not responsible for every thought yours can come up with.

I have this too for as long as I can remember.. As a kid it manifested as an "imaginary friend" but I hated him because he was evil and disgusting and no matter what I did he would not go away.. It felt like i have 2 or 3 people in my mind all fighting and i thought i was crazy..Now I have these obsessive intrusive thoughts and it is a form of OCD.. you might read about that (purely obsessional OCD) and see if its symptoms seem familiar to you..

Don't try to control your thoughts. I used to have the sickest worst possible thoughts as a teen and it grew worse because I realized, "omg how can I think of something like this at such a moment? What's wrong with me?" And then I learned about Ironic Processing, and then any thoughts that came, I let them, and ignored/shrugged them off.

Your thoughts don't define you, it's what you do in spite of them that does. You seem like a good person, so you have nothign to worry about. If you get those thoughts, humor them, think of your mind like a little kid trying to play tricks on you.

"I have no true desire to hurt them, & I love them and would protect them if they were ever in danger"

Then I wouldn't worry about it.

Our imaginations can sometimes run away with themselves. We inadvertently imagine killing someone, f*cking someone, stealing something, destroying something, saving the Nakatomi Plaza from terrorists...

It's normal.

I think I know exactly what's going on with you. There is some entity/demon/what have you that is tormenting you. I have been through this same torment. It's horrible. The first step in getting rid of it is to recognize it's not you, it's this malevolent entity attacking you. I'll give you a link here for a video that helped me a lot. You follow her instructions. When I did it, I actually sensed some dark entity leave my body! And ever since I've felt so much better. https://www.youtube.com/watch?v=8l28m-7SHDE&list=TL6p7kl4q9AbpnCEgSFVMlwMfZ3WqI9Bcj

Obsessive thoughts can be a symptom of anxiety. Try to brush them off. The worst thing to do is give them power by trying to suppress them.
Many times just learning to not worry about them will stop them.

I do it too I was kind of glad to read this because I know I k ow other people do it too though I'm worried I might do it one day because I get kind of jumpy and sometimes act too brash for my own good