It wasn't really that head exploding until he brought up the point of the single player content which was aside from his main point of control issues in fighters.
He is right though... most of the staple moves you need to execute in fighters like SF are motions that are based around stick motions (QCF, DP, HCF, RDP, 360s etc). Doing these motions are harder to do on a D Pad... it always has been like that. Injustice alleviated this by allowing for pad option controls for moves (Down forward instead of QCF).
Like for example... IMO it's easier to do back, back or down down inputs on Pad than stick. There is no reason why fighters can't have forward, forward moves instead of QCF but they don't because QCF has been a staple for special moves for so long due to their origin as arcade stick games. It's not like fighters are unplayable when you have forward forward or back forward moves... that's how 3D fighters operate so you know inputs like those are doable.