I've seen the AI put bounty on my head, and then when the pirates attack me, the AI fleet jumps in and attacks the same planet. So, on the whole, I think building planetary defenses where pirates are known to attack makes perfect sense. It will either handle pirates for you "blindly" or if there is a lot going on, delay the pirate attack long enough for you to move a mobile defense fleet into position. If you play against human players, building planetary defenses where the pirates attack is also a good way to "dissuade" the human player from using pirates as a distraction - if they've scouted your defenses, they'll know that this pirate-distraction tactic won't work with you, and if they didn't scout you, then you'll have a surpise for them.. They'll be thinking you are busy dealing with pirates and boom, all of a sudden, you've got a full sized fleet ready for battle..

Err, but wouldn't you build more than one capital at different times, hence, different levels? So while the higher leveled cap is out doing something, the weak(er) one notches up some exp handling the pirates. I still think this is a better deal (return on investment) than spending money on pirate bounty..

If in 1v1 against the AI and the pirates are becoming a bigger distraction than you would like, it probably means that you didn't have enough planetary defenses. Like I said, putting 3-5 repair bays + 3-5 hangers +  2-3 Frigs/LRMs and you can almost completely "ignore" a pirate attack at the planet.

This is like the Reward Dead or Alive, in the wild wild west It stays there until they bring you in - dead or alive

Give it a try.. Maybe you'll learn to appreciate (if not love) ole Jack Sparrow after a while

OP looks worried about the first raid mainly, and i understand what he means.

If you need to defend from pirates, at the start, you have to stop your colonizing trips (terran/desert have some relatively tough fleets for starting game).

So what i suggest you, is: when you find the pirate base, park a scout on the road from their base to your closest planet (park it on a gravity well with no native fleets ofc). You can leave the other scouting (you should have 2 scouts at the beginning).

This way you can tell when the pirates are coming with a few jumps advantage, enough time to recall your colonizing fleet. No harm will be done to your scout ship as long as you keep it out of their weapons range. They dont bother chasing anything until they get to the designated gravity well (they get a "move order" from the ai).