I remember dog men having this debate 20+ years ago and I suppose it was debated 100 years before that.
One thing I've noticed over the years is that the man who puts some thought into his terriers breeding and is clever about it ie. line breeds, breeds to a working standard, uses the best studs and broods available and culls hard has ALWAYS had a usefull kennell of usefull terriers.
The man who's always swapping and changing, taking a chance on breeding and doesn't care how it's bred always seem's to be the man who always says "It's hard to get a good one" or "I wish I had one as good as ol