No, it isn't.
Because then you'll never beat them = not a solution.
Giving up before a fight even starts ensures you'll never win.
Even if you're pretty sure you're going to lose that warzone, you can try something and see if it works if only for practice, or try and take out one of their players. If you're getting beaten badly it's over quick and you can requeue. The only lasting damage is to your ego and that's all down to you. Longer term, do something to improve your chances individually or as a group.
Very poor attitude.
I second that, even in a match gone completely awry, where our team cannot hold a single node, I usually get at least 5 or 6 medals. (50k dmg, 2,5k hit, 5k hit, 2,5k heal, 10 kills, defended an objective etc, delivering a killing blow).
The only map where I might not get any medals is Hutball, if the enemy premade team has chainpulling sorcs, force speeding, invincible tankasins and leaping juggs. It has happened before that they scored 6 goals in less then a minute.
So, most of the time you actually get stuff out of staying in a losing warzone. And to be honest, I run into premades while solo queuing with such an alarming frequency that if I left every match with a premade on the opposing side, I might as well just stop PvP'ing entirely.