What about my helmet.

What about it? It's not designed to deflect high velocity, giant rounds like those fired by snipers. It'll protect you from small caliber rounds well enough, but a large sniper round will go right through.

Then what's the point of having helmets.

To give you some protection from smaller caliber rounds, as I already said.

It's not fair and should not be allowed.

It is fair and it's in every shooter game ever. Quit your bitching and realize that it's a game mechanic. Don't like something? Think something is OP? DO IT YOURSELF! You'll see that long range sniper head-shots AREN'T the easiest thing ever and AREN'T over powered. Quit whining and just play the game. Or don't play the game. I don't care. But crying "This isn't fair!" at something that has been a core mechanic in shooters for the past DECADE just makes you look like an idiot. That's like saying "It's not fair that he can have more than one gun... it's not fair he can crouch... it's not fair he can sprint" These are all mechanics that are in every FPS, it's not unfair, it's not OP, it's what is to be expected. In fact, if they HADN'T had sniper headshots being one-shots, it would have been underpowered compared to the other specials, which can both one shot very easily. So quit whining and think for a moment before you start crying "OP"...

Some one is mad.

Someone is bad.