I personally welcome the sitution where my team is the underdog. As someone said, this presents "a target rich environment"
... Haven't seen this in CloD often though as I mainly fly blue, but in old Il-2 this is more common, and fun ensues for me much more often.
If the airfield I am taking off from is being attacked, I either make a low level escape to a safe direction and start climbing when I'm certain I'm not being followed, or cancel the take off and choose a safer back field. If I get strafed on the runway, that is entirely my own fault, I should've checked the skies first.
In the event that blues overwhelm the reds, I might switch teams, but I usually take a bomber or a heavy fighter and head for the ground targets and present a nice big target for the reds too.