I do see where you're getting at, however the difference of optifine to forcefield or BSM is massively different. This is because forcefield give you a Massive advantage during fights, able to hit multiple people, you're like god. However this is not the case with optfiine, optifine won't give you those powers to hit multiple people, this still does require some skill to actually beat someone in combat. Instead of having the computer do it for you, you still need to think of some strategies. This has the same affect being compared to BSM, because BSM creates such a significant advantage in combat, being able to sprint while hitting. Because you don't get these advantages with optifine you can't really compare it to BSM or forcefield, because it gives you such a greater advantage over other players.
Optifine also is there for people that aren't lucky enough to get a really good computer, so they cant actually play minecraft at a stable FPS as other people with better computers. This means that people that have bad computers are still able to play with a chance.