SB 10.40.9
sarva eva yajanti tvam
sarva-deva-mayesvaram
ye ’py anya-devata-bhakta
yady apy anya-dhiyah prabho
Translation:
But all these people, my Lord, even those who have turned their attention away from You and are worshiping other deities, are actually worshiping You alone, O embodiment of all the demigods.
Purport:
The idea here is that even those who worship the demigods are indirectly worshiping the Supreme Lord Visnu. The understanding of such worshipers, however, is imperfect.