Did you remove all other unwanted entries or did you just move "Fighter" to the top?
Edited: I was eating a banana and accidentally submitted the reply before I was finished. Ops...
Monster is a vehicle type, like carriers or freighters or colony ships. P-D are an ability granted a component and you can not add abilities to the target list. Your best bet is to create a specialized weapon that will target P-D. Then your fighters will swarm a P-D ship because it is the only legal target. Well that and anything else on the field that has P-D. Nothings perfect!
