My concerns stem from some comments on Duck thinking of elevating them to something more than the regional threat to your civ you want them to be.

If that's not the case than I really have no scruples left if duck is fine with them.

Either way I anticipate your civ mainly since if i'm not mistaken, their likely plan is to reach out to other more advanced societies for help.  How that will play out will be interesting.  

You mentioned them being underdeveloped, does this mean they're very recently space faring?