No, turtles don't hurt much. They rob fish on stringers, sometimes steal bait, become a nuisance when you feed, etc. But they almost never harm a healthy fish. They do however, clean up the mess left by a dying or dead fish. They're the buzzards of the water and perform a fairly useful function.

There are various turtle traps for sale and some innovative ways to trap them if you search this site. Actually having a lot of patience when you hunt them with a 22 works best.