because doing so would land me in a mental institution
Source? Most (Western) countries have requirements like "Must be in acute danger to themselves or others" to involuntarily commit you. Even self harm, as long as it doesn't put your life at significant risk, is insufficient.
Even suicide prevention hotlines don't send tracking information to emergency services as long as you aren't e.g. telling them you will kill yourself right before hanging up.
The fact you've been having these thoughts for 25 years makes me think you weren't in acute danger for (the vast majority of) that time.


This is in reference to people during a psychotic break. They behave irrationally and can be extremely hostile. So yes, unstable people running around in the public with knifes should receive psychological help, voluntary or not. Even if we lived in an anarcho-communist utopia these people will not vanish (although there might be fewer cases due to lower stressors) and must be treated.