The whole point of Fanatic Purifiers is that you want to purge all alien life because you see it as a cosmic mistake. That seems pretty xenophobic to me.Xenophobia isn't only possible background of fanatic purifier.
Why would you refuse to convert them? If it's tied to species then I would qualify it simply as Fanatic Xenophobic.- Religion (Spiritual background) - You are purifying entire worlds of infidels, not intending to convert anyone (Heretics of Dune, Dune Chapterhouse - core classics of SciFi genre). Race doesn't matter
That's just localized mass murder, nothing to do with Fanatical Purifiers.- Rulers will (authoritarian background) - Leader/Governament order destroying world or even entire race for pure power projection (Star Wars, LEXX, WH:40000)
I still see this as xenophobic, the fact that you view other races as useless obstacles is clear xenophobia.- Expansion (materialism background) - Specific race is technologically superior and find other races as useless obstacles is their patch to power. They are removing such obstacles because of pragmatic reasons, and purification-on-sight is considered as most efficient procedure (Unicron, Borg and... Time Lords, before Galifrey Fall)
All the examples you gave were either xenophobic or not fanatical purifiers, not sure I would qualify them as correct examples IMHO.Thing I really hate is lack of imagination - especially when good examples are at hand.