Dish is comm array. Dish not destroyed first = more coalition reinforcements. Dish is heavily armored. Dish needs torps to take it out.

Comm array is the antenna tower. That's what gets reinforcements in. The dish tracks/controls where the warp gate wormholes exit to allow Coalition ships to arrive at their destinations, or spot current Coalition positions in order to direct the warp gate to open a wormhole to allow that ship to return home.

A blast that fries an asteroid should have no problem busting a dish. And if the dish survives, all the tracking/guidance computers and facilities attached to it certainly would not.

Good points.
If you think it through in a military way though, the first and primary target is the dish. That has to be destroyed first to disrupt coalition activity.
The second objective of destroying the asteroid although important (and in some ways more important) is made probably for the reason at worst the dish is gone and at best the asteroid with it.
This is the kind of thing that a command would accept in a real war, the dish out of action to begin with and complete destruction as an added bonus. The fact that the game probably wouldn't let you continue and have you shot is besides the point.
Anyway, that would be my take on the situation.

Skymouse