Nobody can attack an idea, which is merely a memetic pattern. They can, however, attack somebody's potential to retain the idea.
If the idea surrenders, it was merely an opinion. If it fights back, though, it is what some people call “a belief.” In such case, the idea has evolved into a conditioned behavior bolstered by basic conditioning mechanisms (e.g. pleasure or pain).
If you seriously threaten a person's ability to retain a cherished idea they will feel pain. If they manage to hold on to the idea anyway they will feel pleasure. This is how the patterns survive from one generation to the next. It's evolution, pure and simple.
Since the creation of language, and especially since the dawn of civilization, people have confused their authentic selves with memetic patterns. This is why there are religions. This is why there are wars. This is why ... well, you get the idea.
Pavlov's dog was conditioned to drool from its mouth. We humans, it seems, can be conditioned to drool from the brain.
The observations above strike me as trite and obvious. How's that for an opinion?