No. The staff at your LFS are ignorant. There are tons of cichlids that fit perfectly into a community, such as rams, angelfish, discus, and kribs.
The rams may go after your gourami because labyrinth fish and cichlids are closely related. Also, if your rams breed, they will protect their fry from any precieved threat. But, if your tank is large enough, such as 29G+, you should be fine.
Hi there. Like Puma has said, it's possible the rams might chase your gouramis a little. As long as they have plenty of room and you're not overstocked you should be fine. Although make sure you watch the dwarf gourami too, my male dwarf gourami viciously chased my rams so much when they were introduced that I had to put him in isolation!
I have the exact same fishes (a pair of rams and a pair of dwaft gouramis) in my 20 galon planted tank. They live OK for awhile until the rams started breeding, then the ram pair would attack the gouramis. The larger gourami would fight back. Both sides showed some slight damages...At that point, I took the gouramis out for good...
I have a pair of rams and a pair of dwarf gourami in a 29 gallon planted tank and they do just fine with each other. They have been in this setup together since last December. The rams get a bit protective when they have a batch of eggs, but the gouramis have learned to stay away from them during those times and just spend more time up top of the tank. The only other occupants in this tank are 4 otocinclus, whom I almost never see.
I think if your fish have plenty of room to get away from each other, they should be fine.