How we decide to handle this situation will affect our civilisation's culture; there is no chance that performing a genocide will result in no change. All of the genocide options will cause extreme problems in the future.
Simply put, if our civilisation believes so strongly in ending the Zarannists that they'd resort to genocide, it means that they've become intolerant enough to gain a value for it. The Arthwyd will believe in the goodness of wiping out cultures and religions. Every single one of our neighbours has a different culture and religion to us, and they can conflict with ours quite strongly at times. Despite that, peaceful coexistence is possible and will be possible even as we increase our contact with them. However, believing that the Arthwyd should wipe them out will play havoc with that. There'll be more internal pressure to war against outsiders, and more peaceful endeavours such as trade, diplomacy, alliance, tech sharing, and, well, peace will become more difficult.
It'll also cause strife, internal culture clash, and very possibly value degradation. Prior to the latest upgrade, Arthryn's blessing was clashing with our Born Equal value for somewhat obvious reasons, and while fissure in that regard was by no means major now, it would've become major given enough time. Genocide will do the same to Charitable Haven. The more violent forms of genocide will make our people more hostile to other cultures and beliefs, probably axing the value entirely. Relocation will instead corrupt it, turning the value into something similar but worse.
We take in refugees and integrate them as a form of good, and in doing so earn kudos from Arthryn, improve our reputation amongst the poor and needy of the world, and gain value in the form of values, ideas, technology, and even heroes (like Arth) from it. Relocation will turn our refugee acceptance into a weapon. It stops being about giving aid and strengthening the community with the value that foreigners bring to the table. It instead becomes a form of pure economic growth and xenophobic erasure. The intellectual fruits and talents of foreigners will be suppressed with intent just as we'd do now with the Zarannists, and in so doing earn the ire of the most powerful god we know of, who also happens to be our own god.
To summarise, genocide in general will hamper our relations with foreigners. Relocation specifically will downgrade (or remove) Charitable Haven, which will anger Arthryn on account of her being half a foreigner who was welcomed into the community without that community trying to erase her people.
