From the wikipedia article on tachyons:
Most physicists think that faster-than-light particles cannot exist because they are not consistent with the known laws of physics. If such particles did exist, they could be used to build a tachyonic antitelephone and send signals faster than light, which (according to special relativity) would lead to violations of causality.
Why would one consider hypothetical tachyonic particles impossible because of a causality, while leaving wormholes "sound"? Wouldn't messaging or travelling through a wormhole break causality just as communication using tachyons?
Update - CTC breaks down Really fast.. like Planck constant fast. So is it, that communication using tachyons as a carrier will inevitably violate causality.