I doubt he would think to use his weapon against him. Crota may talk a bit but its in a different language and I doubt he's gonna just say his weakness... Not that goku would understand it anyway.
English
-
He could always just instant transmission Crota to Narnia or wherever the hell Crota belongs....
-
If he doesn't know where he's from where's he teleporting him too? Let alone actually fighting him. Sure he could lower his shields but I doubt he'd think to use his sword against him. Odds are he'd break it, toss the pieces (possibly blast those too) st keep trying to hit him with a kameh ha meh ha.