It's a tough philosophical question. Each car has certain mechanical elements that are just fundamental to its character. What's the point of a Corvette with a turbo 4, even if it could be made to make more power than the Chevy small block? (I am well aware that's stretching the laws physics, this is just an example.) There are changes you can make that are consistent with the character of the vehicle, such as putting the 2.5 liter flat four from an STi into a regular WRX or an old RS. That's more like keeping the same person, but sending them to the gym for a year. It's still unmistakable Subaru.
But what if you get rid of AWD? Now, one of the key engineering features that distinguishes Subaru vehicles is gone. I think you've lost an element of harmony, of wholeness. To make an analogy, if the car is a knife, I wouldn't try to turn it into an axe. I'd just sharpen and hone the knife. I wouldn't make a RWD Subaru.
But that wasn't your question. Your question was does it bother me when others do it. I'd say no, not really. They're opening up for themself a whole new world of what can be done with a Subaru. Very often, people are putting a lot of effort, engineering, and fabrication into these creations. I can respect that. Besides, it's a free country. I sure wouldn't want them dictating to me what I could or could not do with my car.
CN: I wouldn't convert a Subaru to RWD because it does not fit with my vision of engineering harmony. I do not feel bad about others who do it because it's a free country. Uh, live and let live.