Schlissel certainly believed he was following in the footsteps of Pinchas and doing a good deed. He was not wantonly killing to willfully indulge his yetzer hara to murder someone. He may have been misguided and wrong, and if so it is certainly his fault that he did not better educate himself, but how does this mistake make him not Chareidi?
It sounds like it is obvious to most of the posters here that there is no comparison between Schlissel and Pinchas, yet do any of you have a source which explicitly says that the halacha of “kana’im pog’im bo” does not apply nowadays? If not, what kind of acts would you agree do warrant someone killing the perpetrator of? If a prominent Jewish leader were to publicly and willfully have relations with a non-jew (exactly what Zimri did), and someone who is genuinely motivated leshem shamayim would kill them, would that be wrong? If so, how is that different to what Pinchas did?