Kicked from bg

I was just playing a bg (Arathi Basin) and I got a call during the preparation phase, when I came back (roughly 30 secs after the beginning of the battle) I had been reported for afk. The game said that I had to enter pvp combat or I would be kicked, until this point all was fine. I entered combat, killed a guy and died, the effect didn't disappear, I entered combat again and while fighting I got kicked from the bg.

Would someone mind explaining why the **** do I get a message saying that I must enter pvp combat to prevent from being kicked if I will be kicked anyway? If so, kick me straight away, don't put random useless effects.