So what if you raise the hand and get 5 callers. When that happens you at least have a better grip on table image. It's loose man. Time to trap some busters. When the table is loose like this I play premium hands and drawing hands. Then again maybe it was just a strong deal. Raise again preflop next time you get one of these sub premium hands and see how many callers come in. You might be pleasantly surprised to find yourself isolated. If not then you gotta play the loose table against it's own grain. Fold those hands and then when it tightens up start gleefully isolating with them again if that's your fancy.

From the sounds of your situation it was just a loose table because it was a freeroll with new bad players. You can't chase the bad players out of a pot, you can only lose to them short term and win longterm when they chase enough ghosts.

Don't get mad, just adjust your game according to who your playing against. The higher the stakes, the better the isolation. It's whole different ball game. It took me a while to understand why great players don't like playing new players. I understand completely now. You can't outthink a sponge.