Canon Towers destroy friendly towers.

The splash damage from Canon Towers apparently damage everything, including other towers you own. I don't remember this from regular Warcraft, but maybe that is why they aren't used much. I remember them damaging friendly units, but not ripping your base apart too.

Anyways I can't make it stop. I turned on Enemy under the Area of Effect Targets setting hoping it would limit it to enemy units of course, but it didn't do anything. Could I use Spill Radius to get an AOE attack, or what does that do?

On a side note, what is the difference between Artillery and Missile weapon type?

Look at the Area of Effect targets, remove the "Structure" classifacation and the AoE won't hurt structures anymore.

Artillery attacks are always directed against the ground and can use the Attack Ground ability, they also miss moving targets, Missile attacks do not.

Ya I guess I don't need splash for structures, that works.

Thanks for the info on artillery.

Or just disable friendly units.

Friendly units isn't enabled.

You should be able to make it not affect allies by changing the splash targets to add enemy and neutral, but you said that doesn't work.

Then enable enemy units