The argument about Israel's right to exist is dishonest because it's explicitly meant to be equated to Jewish existence.
The easiest way to shut down this nonsense is to ask for some contemporary examples of countries that don't have the right to exist. And if they come up with one, Iran is popular, ask them why Israel expects peace while her policy toward her neighbors is annihilation. This is obviously bad faith, but they'll be forced to deconstruct their own argument to call you out.
I love it that even among Linux users there are proselytizers that annoy everyone else. You'd think that switching to Debian or something would inoculate you from pretentious nagging to switch OS, but NOPE!
(I'm just salty because Valve didn't pick my fav distro.)