I've never met a single person named Arthur and I've read several books with characters I liked named Arthur--all of which makes me like it. I definitely see the old-fashioned feel that it has, but I still like it. I think it would be reasonably well received in my area.
Arthur Weasley is my fictional husband---just so you know.
I think Arthur is excellent. As others have pointed out, I think it's just a matter of what's currently in style. We're starting to see a resurgence of stately classics like Henry and Oliver, but a majority of parents are still on board with the two syllable, probably Irish or Scottish, ends-in-"n" names. I think growing interest in vintage names and the -"er" names (Asher, Archer, Harper, etc) will give Arthur a boost in the next five to ten years.
I really like Arthur although I don't think I would use it as a first but it's a possible middle.
I mentioned Arthur to my mom today and she was not into it because "people would call him Art". Um, maybe in the 1950s or whenever you're from, mom. I don't know, I don't see Art and Artie as such natural nicknames of Arthur that people would start using them without even being given the go-ahead to do so. They're no "Mike" or "Matt," you know?
I've also seen some objections due to Arthur the aardvark, and I think because it was in the top 100 from 1880-1969 it does give off an old man/middle-age vibe to some. Every other objection I've heard - that I can think of - relates purely to aesthetics and simply not liking the sound of it.
Personally, though, I love Arthur. I don't expect that you'll be getting uniformly negative reactions on this board, and I'm actually surprised that you've gotten so much hate irl. Arthur really didn't click with me until I actually encountered a kid named Arthur, though...maybe that's all the Arthur-bashers you know need to change their minds?
I love Arthur. It's masculine but sweet :)
I love Arthur! But I love other names more.
I know a ten-year-old Arthur. He is very athletic and a clever boy.