Alien campers? That's even lamer then Human campers :eek: Haven't seen aliens camp. Sure they feed the humans and such but haven't seen them camp.
They don't camp in their base. They camp outside of the human base.
Indeed, when aliens camp outside the H base, it sucks.
An interesting stratergy to stop H camping is to just camp yourselves. Once you know they're not moving, get everyone to stay in the base and see if you can build that
perfect base.
Move the base, repaint the walls, chat about your favorite mode of transport or whatever. Entertain yourselves until the humans get bored.

Just leave them there, tensed for attack.
After about five or so minutes, the entire alien team will have Goons, which will slaughter anyone who enters the base, so you'll get loads of kills without allowing them to progress.
Because seriously, no s1 weapon can protect against 5 goons.

Just don't leave your base and stay to the side of doorways, ready to pounce. (When they start coming.)
Make sure you don't meet in mid air.

While you're waiting for them, you could set up a roter. ;P