I understand why a lot of people don't like what the puzzle piece can potentially represent. I used to feel exactly the same way. But over time I've come to actually really like it - Firstly, I like puzzles. Really, really like them. Both the kind that are made of cardboard and have a picture on them, and also the type that involves life*. Solving puzzles keeps life interesting.
Secondly, instead of seeing the puzzle piece as indicating that I'm a puzzle myself, I see it as the final puzzle piece to be fit into a full understanding of myself. Something like "oh! that's why I act/thing like that!" Autism is the missing puzzle piece I've been looking for for so long.
Finally, the human brain in general is so incredibly poorly understood that it's exciting to see the developments in science trying to understand it. And just as we're so incredibly behind in understanding glial cells compared with neurons, we're also behind in understanding the autistic brain compared with NTs. As a former neuroscientist I'm biased, I'm sure, but the puzzle piece symbolises for me a quest for knowledge and understanding far more than it denotes hostile confusion.
Again, I get why some are against what the symbol can represent, and I've certainly heard many explanations of it that is at the least humorous and at the most offensive, but people are going to be ignorant or offensive anyway, regardless of what symbol is used.
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*Footnote: Like being hundreds of miles away from where you expected your cross-country buss to drop you off and having to figure out the most economically viable and time-efficient way to get back to where you want to be.