...well, there's violin in several strains of metal for good reason. Folk metal or metal influenced by folk music has the fiddle in it because, well, frankly, it adds a folk edge to it. It can be done well or done badly depending on the band Primordial and Skyclad always seemed to do it well.
Some doom metal have the violin because it can sound incredibly mournful and desperate, as with My Dying Bride...but a lot of this symphonic limp wristed nu-goth stuff have the violin because (and no offence, ladies) "chicks dig it".
I don't think the violin in metal is a problem. The main problem is with crappy synths. Why do they do that ?