Those who adhere to the Omnigod conceptualization approach God from an all-or-nothing perspective. God is either Omni, or He is not a god at all. Moreover, they accuse those who do not accept the Omnigod idea of committing a category error stemming from anthropomorphism.
God is God, and man is man. One is the supreme, absolute, self-sufficient Creator capable of anything; the other is a mere creature, finite, mortal, utterly contingent, with limited capabilities.
Considering these two disparate natures, it is readily evident that God and man are not and cannot be in the same category of being. Furthermore, those who suggest that God and man are in the same category think far too highly of man and far too little of God. Non-omni God is just hyper-anthropomorphism -- excessive projection of human traits and characteristics onto the Divine.
Those who subscribe to Omnigod theology declare that only Omnigod is worthy of worship. Put another way, if God is not omni in every conceivable way, He is just a being among beings and essentially unworthy of reverence, devotion, exaltation, praise, etc.
If He is just a being among beings, He cannot expect us to obey Him or feel duty-bound to Him. Nor can he expect us to love Him. If God is not Omni, He cannot command such things and should not expect to receive such things from us.
Omnigod believers accuse those who do not believe in the Omnigod philosophy of errant, arrogant, hubristic anthropomorphism that elevates man far beyond his station in Creation; however, they rarely stop to consider that their vehement refusal to consider relations with a non-Omni God might mark the very pinnacle of human error, arrogance, and hubris.