Probably the difference of opinion comes from different meanings of the word "mutt" -- it can mean a mixed breed, it can also mean an inferior dog, a mongrel, a stupid person, etc.....So, it is easy to see why some might think the term derogatory. Me.... I have used it as a weird term of endearment for my babies, "
come here you lovable mutt" -- when they are all AKC registered and some with pretty nice pedigrees. But they came and gave me kisses just the same.
I am against purposely mating different breeds together but that is just my preference. I love Yorkies for what they are. I love other breeds for what they are too. I have a purebred Dachshund and a purebred Jack Russell that I love dearly as I have my unpapered mixes along the years.
But I think if a person has a great example of a breed, they should not dilute that. I have seen some websites with yorkies being sold that look suspiciously like there were some mixed breeds in the woodpile. One site in particular sold yorkie-wawas or something and some of their yorkies looked as much chihuahua as the mixes being sold. How do you trust that? Another puppy might look all yorkie, only to have puppies that looked as mixed as all get out.
But I do not think my opinion is the only one on this subject. There must be a lot of people who love the idea of mixing the breeds or they would not be selling. So, maybe it is a way of coming up with new breeds for the future -- or diluting the fine purebreeds we have now -- I guess we will see in a few generations. Some day in hind sight, the answer may be more clear.