Jooce, these guys weren't trying to be an *** to you or your friend it's jsut the game has gone past the line for when features could be added and removed (Saw it in one of Wiliamson's blog things he does in the news and announcments section) they're also right.
Disabling head bob would give players an advantage they would be able to see clearer while moving whereas people who had it enabled would not. Motion sickness is also easily overcome (compared to my fear of flying; that was an expensive fear to get rid of

)
The simple fact is the whole game can't be changed for one persons needs and as someone stated already the game ships with mod tools so you could always make a mod without head bob and even run a server for all other sufferers, if what Panzer Jager has said is true then you could possibly fill a small server with motion sick people and you could be the hero who made the head bob mod
P.S-Although some of my humour may seem trollish i am not trying to, i'm just English we have that effect on people in normal speech.