It'd be like reading someone's diary, wiretapping them, or taking secret pictures of them in the shower.
It'd be stronger than that, or at least more comparable to your last example, since one of the key components of forced mind-reading is that the person whose mind is being violated is powerless to stop it - they can't stop it, because it's magic. Magic isn't something that most people (non-magic people) can fight against.
Not to mention that mind reading compromises freedom of thought. Not even expression, but thought, the possibility to even think things to yourself. I can't even call it the first freedom, because it's a freedom that's impossible to take away in our world. Not even the most totalitarian regime is going to know what you think in your heart of hearts. Mind reading rips that safety away.
So while I wouldn't call it 'rape' without qualifier, and while I do understand why the term 'mind rape' is uncomfortable, I personally don't reject the term.