Ah, the way I took it was that if profilers think that stabbing is a substitute for rape, then Foyet was (conceptually) raping Hotch by stabbing him--so either Hotch has to stop profiling like that ("will you still think that after this" line) or he himself is a rape victim; with Hotch being so strong and self-reliant, I think that thinking of himself as a victim of anything, much less rape, would be devastating.