Servants have shown the ability to interfere with space and spatial effects without MR or some sort of ability.
Such Heracles swatting Caladbolg, or breaking Enkidu.
Hence servants can probably break through space and hurt Accel.
At least I think that's what he's arguing.
I really don't want to get into the discussion of Fate vs ToAru number 1000 but that should not overcome the Accelerator field.
Leaving the stats aside and discussing some space bullshit.
-Accelerator on base faced and reflected back Gabriel's physical attacks, when it is mentioned that Gabriel's presence already distorts reality.
-With one fist, Coronzon was able to break the space between two different timelines to cross them, but she physically couldn't overcome Accelerator's (base) field and had to use special magic against vectors to damage him.
-He deflected the cuts of the Curtana that can slice through space, slice through upper and lower dimensions, slice between phases, cut the fabric of the universe, and distort space, though Elizard thought that if she constantly attacked at some point she would overcome Accelerator's field but never managed to do it.
-He deflect the teleport and when it happens, strange phenomena appear in space, he can also prevent things from teleporting him and making a space cut like Kuroko and Awaki can do too, the only time a teleportation affected him was because a robot had specific calculations to overcome Accelerator's field and it was not only teleportation but also other types of attacks such as telekinesis, but at the end of the fight it is seen that he can no longer affect Accelerator so it is understood that he corrected that weakness.
And no, I'm not saying that Accelerator is immune to any space hax but space slicing, breaking space and distorting it are things he can deal with even on base.