There are many different Moshiach scenarios. Which one of them will actually occur depends on us now!
There is a scenario of a seemingly natural, slowly enfolding over years Messianic Age, in which the Erev Rav and goyim will try to kill the Moshiach in the early days of his hisgalus: "...by dedicating the Third Temple, like his ancestor David, Messiah will suffer persecution at the hands of skeptics and scoffers, who will refuse to recognize his sovereignty and will scheme to assassinate him to destroy his monarchy..." (Artscroll, intro Tehillim 53)
And one reason for this could be their desire to prevent a return to the "Tanach Era of sacrificial animal butchery". If the Rubashkin saga, PETA, Animal Rights and anti-shechitah movements are anything to go by, this desire will literally be ...to the death!