The person you're responding to isn't asking for a material proof.

They're pointing out that ontological arguments are typically seen as an "argument of last resort" in a philosophical setting, and are making an (abductive) argument that the use of an ontological argument indicates a weaker position than the importance of the proof (the existence of a god) would otherwise suggest.

In which case you have no claims

The only claims possible are material

Please demonstrate to me a non-materialist claim that has no impact on the materialist world, and still complies with a conception of an omnipresent God

I can conceive of a greater God which does have a material existence, so I think it's valid to request material proof.

the claim (sqrt(2) being irrational) needing material evidence can be reduced even further to the number two needing material evidence. I'm not posing this either for/against your argument, just saying at some point you can doubt the existence of 2 itself. (handing me 2 items doesn't count, what is ... two?)