Killing all of them will be hard, the odds are I simply kill enough of them to send them running far from my reach.
In Islam, Mohammed has been revealed as the prophet to both djinn and man. Considering that, in 20-30.000 years noone saw a single lizard person (because there's no aliens in the Duniverse. There's at best the Tleilaxu and the Guild Navigators but they're just GMO humans altered either in a lab or by exposing themselves to MASSIVE doses of melange) and that djinn likely made it into Fremen mythos (they're still pseudo-Muslim and they're mentioned in the Dune Encyclopedia), I guess that nobody ever saw aliens coming and that if they will be seen, the results may be unpredictable.
As for Zen Buddhism, I just don't know enough about it so I wont speak, but I'd rather stay away from stereotypes.
Consider this: mankind in the Duniverse IS quite genocidal. They launched a crusade against every sentient, thinking machine, because a bunch of them who managed some hospitals on Richese were aborting babies without having their moms know about it. They waged war against them, destroyed ALL OF THEM (thinking, sentient AIs and even people within machine bodies) and forbid computers from being developed ever again. As a result, most of the functions that we usually delegate to calculators or computers are performed by mentats, people who are trained to think as fast and efficiently as computers.
People can be true assholes there.