He said that he would not recommend using a Micro T1 on an assault rifle, like the M4, because it's field of view is more narrow than a Comp M4 and it would not provide as easy an aquisition of targets as the CompM4.
Wow, that's ignorance at it's best right there. As others have pointed out already, both are intended to be shot with both eyes open meaning that they both have an unlimited field of view. Beyond that, if you look at technical specs they both have 30mm objectives meaning there's no physical way for the field of view to be any different. And having shot both, I'd say if anything the T-1 is actually allows for a clearer field of view because there is less housing around the optic to obscure your vision. So you're gut response was correct: The guy didn't know what he was talking about...