That's literally what happened 7.000 years ago with Dath'remar Sunstrider. Malfurion and the druids banished him and his Highborne because they conjured a terrible magical storm over Ashenvale, which greatly threatened Night elf lands. Dath'remar abandoned his homeland and founded a new kingdom, and then established contact with the Human nations and built new alliances with them.
History has come full circle, only this time it's Dath'remar's people who are acting as the self-righteous, xenophobic, short-sighted hypocrites. The only reason why the blood elves were not butchered down to the last child during the Fourth War is because Alleria still feels connected to Silvermoon. Otherwise there was nothing stopping Alleria from just teleporting inside the Sunwell Plateau to corrupt the Sunwell again. If anything, Theron and Rommath should thank her for her mercy, before begging for forgiveness.