If the enemy just wants to sit in their base (Even if you give them ample room and time to move out) there is only a few things you can do:
Fbomb the crap out of the base, I'm sure 6 people all doing this would not only look good but be very effective in at least moving them into their hanger and looking more cowardly.
ERPPC/LG spam. Get everyone into mechs with ERPPC or LG sit as far away as possble. Pick off the enemy mechs, or even the turrets if you get that bored.
On thunderrift, it's going to be more of a case of brute force running headlong into their base taking out their turrets asap and camping their base for 1-5min blowing them all up, and then running away so you don't spawn rape...... This is impossible at the start of the game mind you, but if they camp at the start I would just find another server.
Either way it's going to end up with one team camping, and the other team being cheap and cheesy to actually do anything all game....