"Showing" anger can be dangerous to you. Part of you correctly recognizes that. It is just how you show it. If you can put it into words (which is what therapy is for), that is a way to show it, that should be safe(r). Maybe we think in words, so that if you can put it into words, you can think it too. If you can think it, it will not be so dangerous. If you cannot admit it even to thought, it will become all the more powerful. That is where the eventual danger is, in not being able to think it, because then it will get more powerful and can burst out in ways which are dangerous (to you).

If you can think your anger, put it into words, even just inside yourself, then you have more choice in how you express it outside, rather than having it control you.