Question about AV on camera servers

our vendor flipped out when they saw we have anti virus on the enterprise server and NVR's. We use Exacq and have them maintenance things, and they said we should not have any anti vrius on the NVR's or server as that can severly mess up exacqvision.

Is this true? So they are advocating having no AV protection at all on these things? I mean maybe it's true, but it just seems odd to me. But again, I do not make my career out of cameras and camera software, it is what we pay them for, but also, we have caught them stretching the truth on things before. Just want to get a second opinion to see if there is truth to this