There is a difference between line breeding and inbreeding. Or rather inbreeding is the most extreme form of line breeding, Father to daughter, Mother to son , Sister to Brother etc. IMO its to close, but then again, if nothing on either side is too close you should avoid to many problems. The problem with it is when you get people with little knowledge of breeding, repeatedly doing it with no out crosses your sure to have trouble . Nothing shocking about it, the working world is far more rife with close breeding's than the pedigree world.