I have no problem with the word aspie. I use it myself sometimes.
It's just more convenient sometimes to use the word aspie rather than the long version. If I'm explaining or discussing something long about Asperger's syndrome, I might say "people with Asperger's syndrome" a couple of times at first, but then switch to the short term, aspie, because saying "people with Asperger's syndrome" repeatedly just ends up sounding too pretentious, long and hard to take in. Aspie is a shorter and easier word to use. That's the main reason why I use it.
To me the word aspie also sounds more like a human variation rather than some defect or a problem that will send some NTs on a race to try to "fix" us or dehumanize us by treating us like a disorder rather than people. I don't deny that AS is a disorder, but I don't need to be treated like a disorder all the time. AS stays with us throughout our life and can't be "fixed" and we have our good and bad sides like NTs do, so in daily talk I'd rather think of it as a variation rather than some big ass disorder with a long, strange name that people make lame jokes about all the time (ass burgers, asparagus
).