Here's a great idea,
How about any Qantas pilot who feels it necessary to advise some bloke flying a 310 in the Territory that they will "be making a better long term decision about (their) careers by rejecting Jetstar now, staying another 12-18 months in GA", tenders their resignation immediately and allows the GA bloke to take their QF position.
That way they can show all the other GA pilots just how "valuable" they really are (OMG, a former Qantas pilot is in town!) and also the GA pilot can have the only job he or she may be allowed to accept under your narrow, utopian view of the world.
There's an old saying out there, gentlemen - "Fight your own battles". Asking GA pilots to refuse employment with any airline is a little bit too much like what Cathay pilots did to their "colleagues" after the 49ers dispute.
The world won't go out of its way to protect you or (like you give a stuff) "the industry". You have to do that all on your own.
As longjohn quite correctly said, you "should be trying to engage the Jetstar pilot group" - we are more than amenable to it but by virtue of numbers aren't able to instigate an effective campaign - there are 2500 of you and 300 of us. What's worse - our existence or your inaction?